Basically same idea, but two separate controllable asymmetric current mirrors, rather than one, and no current steering. The half-wave
rectifier still seems to be the source of the distortion in the
stabilised output.
C25 and C26 take out as much of it as I can. Increasing them - from 15nF
to 33nF makes the distortion worse. Splitting the resistors into three
rather than two and adding two more capacitors might help, but what this circuit needs is more insight, rather than more components.
On 10/02/2025 5:18 pm, Bill Sloman wrote:
Basically same idea, but two separate controllable asymmetric current mirrors, rather than one, and no current steering. The
half-wave rectifier still seems to be the source of the distortion in the stabilised output.
C25 and C26 take out as much of it as I can. Increasing them - from 15nF to 33nF makes the distortion worse. Splitting the
resistors into three rather than two and adding two more capacitors might help, but what this circuit needs is more insight,
rather than more components.
Splitting the resistors did help, and the optimum capacitor value at C25, C26, C27 and C28 turned out to be 4.7nF. The second and
fifth harmonics were just 80dB below the fundamental and the third 91dB down. Not dramatically good, but respectable.
Other changes were less succesful - the current nmirror approach does suffer from the need to split the waveform in order to
generate the asmplitude correction waveform and minimising the 2usec wide switching spikes that show up at cross-over is what it
takes to get it to work tolerably well
I've swapped out the LT1115 for the LT1678 - that doesn't seem to suffer from parasitic oscillations in LTSpice 24, so it should
simulate tolerably fast.
"Bill Sloman" <bill.sloman@ieee.org> wrote in message news:voh7a5$26aqj$1@dont-email.me...
On 10/02/2025 5:18 pm, Bill Sloman wrote:After fixing line wraps I had to move U1 down into position.
Basically same idea, but two separate controllable asymmetric current mirrors, rather than one, and no current steering. The
half-wave rectifier still seems to be the source of the distortion in the stabilised output.
C25 and C26 take out as much of it as I can. Increasing them - from 15nF to 33nF makes the distortion worse. Splitting the
resistors into three rather than two and adding two more capacitors might help, but what this circuit needs is more insight,
rather than more components.
Splitting the resistors did help, and the optimum capacitor value at C25, C26, C27 and C28 turned out to be 4.7nF. The second and
fifth harmonics were just 80dB below the fundamental and the third 91dB down. Not dramatically good, but respectable.
Other changes were less successful - the current mirror approach does suffer from the need to split the waveform in order to
generate the amplitude correction waveform and minimising the 2usec wide switching spikes that show up at cross-over is what it
takes to get it to work tolerably well
I've swapped out the LT1115 for the LT1678 - that doesn't seem to suffer from parasitic oscillations in LTSpice 24, so it should
simulate tolerably fast.
I then noticed an issue with C10 so I converted to ANSI in Notepad++ and saved the file.
Simulation then failed without giving any clue what was wrong.
But instead of spending hours tracing the problem I removed .ENDS from the BAS70 model.
Simulation now runs fine at about 44 ms/s in LTSPice 24.1.2
FFT is approaching 60dB
Simulated circuit included below.
I can get 80dB by adding an LC tuned circuit to a simple phase shift oscillator of the type which turns up here:
https://www.google.com/search?q=sine+wave+oscillator&udm=2
No gain control yet but for unknown reasons it does run at constant (unpredictable) amplitude with very critical emitter resistor
adjustment.
I'm thinking of trying the sample/hold method posted by JM but with real components.
So I need to turn a FET on (not sure for how long yet) at the peaks of the sine wave.
On 14/02/2025 1:45 am, Edward Rawde wrote:
"Bill Sloman" <bill.sloman@ieee.org> wrote in message news:voh7a5$26aqj$1@dont-email.me...
On 10/02/2025 5:18 pm, Bill Sloman wrote:After fixing line wraps I had to move U1 down into position.
Basically same idea, but two separate controllable asymmetric current mirrors, rather than one, and no current steering. The
half-wave rectifier still seems to be the source of the distortion in the stabilised output.
C25 and C26 take out as much of it as I can. Increasing them - from 15nF to 33nF makes the distortion worse. Splitting the
resistors into three rather than two and adding two more capacitors might help, but what this circuit needs is more insight,
rather than more components.
Splitting the resistors did help, and the optimum capacitor value at C25, C26, C27 and C28 turned out to be 4.7nF. The second
and
fifth harmonics were just 80dB below the fundamental and the third 91dB down. Not dramatically good, but respectable.
Other changes were less successful - the current mirror approach does suffer from the need to split the waveform in order to
generate the amplitude correction waveform and minimising the 2usec wide switching spikes that show up at cross-over is what it
takes to get it to work tolerably well
I've swapped out the LT1115 for the LT1678 - that doesn't seem to suffer from parasitic oscillations in LTSpice 24, so it should
simulate tolerably fast.
I then noticed an issue with C10 so I converted to ANSI in Notepad++ and saved the file.
When I picked up your text file, I noted that C10 (on the output of U4, the LTC6655-1.25 voltage reference) had gone back to 3.3 -
no suffix. I set it back to 3300n(F) and the circuit worked as it did for me with the harmonics mostly 80dB down with the third
harmonic about 91dB down
Simulation then failed without giving any clue what was wrong.
But instead of spending hours tracing the problem I removed .ENDS from the BAS70 model.
I put it back in again. and it didn't make any difference to my simulation.
Simulation now runs fine at about 44 ms/s in LTSPice 24.1.2
FFT is approaching 60dB
Not having the right value capacitor at C10 usually totally messes it up. We've had that issue before.
Simulated circuit included below.
I can get 80dB by adding an LC tuned circuit to a simple phase shift oscillator of the type which turns up here:
https://www.google.com/search?q=sine+wave+oscillator&udm=2
Where? There's a lot of stuff there.
No gain control yet but for unknown reasons it does run at constant (unpredictable) amplitude with very critical emitter resistor
adjustment.
It's probably relying on the change in current gain with changing collector-base voltage. It is a small effect - the Early
effect - and non-linear.
I'm thinking of trying the sample/hold method posted by JM but with real components.
So I need to turn a FET on (not sure for how long yet) at the peaks of the sine wave.
Sample and holds tend to put spikes on the supply rails. Keeping them out of the output can take a lot of work.
"Bill Sloman" <bill.sloman@ieee.org> wrote in message news:vol49p$2vd0d$1@dont-email.me...
On 14/02/2025 1:45 am, Edward Rawde wrote:
"Bill Sloman" <bill.sloman@ieee.org> wrote in message news:voh7a5$26aqj$1@dont-email.me...
On 10/02/2025 5:18 pm, Bill Sloman wrote:After fixing line wraps I had to move U1 down into position.
Basically same idea, but two separate controllable asymmetric current mirrors, rather than one, and no current steering. The
half-wave rectifier still seems to be the source of the distortion in the stabilised output.
C25 and C26 take out as much of it as I can. Increasing them - from 15nF to 33nF makes the distortion worse. Splitting the
resistors into three rather than two and adding two more capacitors might help, but what this circuit needs is more insight,
rather than more components.
Splitting the resistors did help, and the optimum capacitor value at C25, C26, C27 and C28 turned out to be 4.7nF. The second
and
fifth harmonics were just 80dB below the fundamental and the third 91dB down. Not dramatically good, but respectable.
Other changes were less successful - the current mirror approach does suffer from the need to split the waveform in order to
generate the amplitude correction waveform and minimising the 2usec wide switching spikes that show up at cross-over is what it
takes to get it to work tolerably well
I've swapped out the LT1115 for the LT1678 - that doesn't seem to suffer from parasitic oscillations in LTSpice 24, so it should
simulate tolerably fast.
I then noticed an issue with C10 so I converted to ANSI in Notepad++ and saved the file.
When I picked up your text file, I noted that C10 (on the output of U4, the LTC6655-1.25 voltage reference) had gone back to 3.3 -
no suffix. I set it back to 3300n(F) and the circuit worked as it did for me with the harmonics mostly 80dB down with the third
harmonic about 91dB down
Simulation then failed without giving any clue what was wrong.
But instead of spending hours tracing the problem I removed .ENDS from the BAS70 model.
I put it back in again. and it didn't make any difference to my simulation.
It will for anyone else using 24.1.2.
I note that the model for MMBF4391 is still present and does not have .ENDS so why should BAS70 need it?
In 24.1.2 you get errors which make no sense and do not mention BAS70.
Simulation now runs fine at about 44 ms/s in LTSPice 24.1.2
FFT is approaching 60dB
Not having the right value capacitor at C10 usually totally messes it up. We've had that issue before.
C10 is 3.3uF
Changing to 3300n and resimulating makes no difference. Definitely only 60dB difference between 1kHz and 2,3,4,5kHz
Exact circuit I'm simulating (in 24.1.2) included below.
Simulated circuit included below.
I can get 80dB by adding an LC tuned circuit to a simple phase shift oscillator of the type which turns up here:
https://www.google.com/search?q=sine+wave+oscillator&udm=2
Where? There's a lot of stuff there.
Phase shift oscillator with feedback from the collector through CRCRCRCR to the base.
No gain control yet but for unknown reasons it does run at constant (unpredictable) amplitude with very critical emitter resistor
adjustment.
It's probably relying on the change in current gain with changing collector-base voltage. It is a small effect - the Early
effect - and non-linear.
I'm thinking of trying the sample/hold method posted by JM but with real components.
So I need to turn a FET on (not sure for how long yet) at the peaks of the sine wave.
Sample and holds tend to put spikes on the supply rails. Keeping them out of the output can take a lot of work.
Yeah I've had that problem before, decades ago.
A capacitively coupled inverted sampling signal was able to sufficiently remove the problem of the sampling signal appearing in the
output.
But that may not work at 140dB down.
Here is the exact version of your circuit from my most recent simulation of it.
On 14/02/2025 5:24 am, Edward Rawde wrote:
"Bill Sloman" <bill.sloman@ieee.org> wrote in message news:vol49p$2vd0d$1@dont-email.me...
On 14/02/2025 1:45 am, Edward Rawde wrote:It will for anyone else using 24.1.2.
"Bill Sloman" <bill.sloman@ieee.org> wrote in message news:voh7a5$26aqj$1@dont-email.me...
On 10/02/2025 5:18 pm, Bill Sloman wrote:After fixing line wraps I had to move U1 down into position.
Basically same idea, but two separate controllable asymmetric current mirrors, rather than one, and no current steering. The
half-wave rectifier still seems to be the source of the distortion in the stabilised output.
C25 and C26 take out as much of it as I can. Increasing them - from 15nF to 33nF makes the distortion worse. Splitting the
resistors into three rather than two and adding two more capacitors might help, but what this circuit needs is more insight,
rather than more components.
Splitting the resistors did help, and the optimum capacitor value at C25, C26, C27 and C28 turned out to be 4.7nF. The second
and
fifth harmonics were just 80dB below the fundamental and the third 91dB down. Not dramatically good, but respectable.
Other changes were less successful - the current mirror approach does suffer from the need to split the waveform in order to
generate the amplitude correction waveform and minimising the 2usec wide switching spikes that show up at cross-over is what
it
takes to get it to work tolerably well
I've swapped out the LT1115 for the LT1678 - that doesn't seem to suffer from parasitic oscillations in LTSpice 24, so it
should
simulate tolerably fast.
I then noticed an issue with C10 so I converted to ANSI in Notepad++ and saved the file.
When I picked up your text file, I noted that C10 (on the output of U4, the LTC6655-1.25 voltage reference) had gone back to
3.3 -
no suffix. I set it back to 3300n(F) and the circuit worked as it did for me with the harmonics mostly 80dB down with the third
harmonic about 91dB down
Simulation then failed without giving any clue what was wrong.
But instead of spending hours tracing the problem I removed .ENDS from the BAS70 model.
I put it back in again. and it didn't make any difference to my simulation. >>
I note that the model for MMBF4391 is still present and does not have .ENDS so why should BAS70 need it?
In 24.1.2 you get errors which make no sense and do not mention BAS70.
The BAS70 model dates back to 2015. It's a classic Spice model - and LTSpice is supposed to run them.
Simulation now runs fine at about 44 ms/s in LTSPice 24.1.2
FFT is approaching 60dB
Not having the right value capacitor at C10 usually totally messes it up. We've had that issue before.
C10 is 3.3uF
Changing to 3300n and resimulating makes no difference. Definitely only 60dB difference between 1kHz and 2,3,4,5kHz
Exact circuit I'm simulating (in 24.1.2) included below.
And when I run it (after having put U1 back where I intended it to go and restored it's connection to the negative rail) I got the
second to the fifth harmonics harmonics 80dB below the fundamental with the third 91dB down. When I stretched the frequency
display out to 100kHz the higher harmonics were going down.
I did let it settle down for two seconds before taking the FFT of V(out) onver the next second or so.
Simulated circuit included below.
I can get 80dB by adding an LC tuned circuit to a simple phase shift oscillator of the type which turns up here:
https://www.google.com/search?q=sine+wave+oscillator&udm=2
Where? There's a lot of stuff there.
Phase shift oscillator with feedback from the collector through CRCRCRCR to the base.
That is the simplest phase shift oscillator. Why didn't you identify it when you first mentioned it?
No gain control yet but for unknown reasons it does run at constant (unpredictable) amplitude with very critical emitter
resistor
adjustment.
It's probably relying on the change in current gain with changing collector-base voltage. It is a small effect - the Early
effect - and non-linear.
I'm thinking of trying the sample/hold method posted by JM but with real components.
So I need to turn a FET on (not sure for how long yet) at the peaks of the sine wave.
Sample and holds tend to put spikes on the supply rails. Keeping them out of the output can take a lot of work.
Yeah I've had that problem before, decades ago.
A capacitively coupled inverted sampling signal was able to sufficiently remove the problem of the sampling signal appearing in
the
output.
Reduce rather than remove. Cancellation schemes rarely work perfectly.
But that may not work at 140dB down.
Here is the exact version of your circuit from my most recent simulation of it.
Give or take the usual problems.
--
Bill Sloman, Sydney
On Fri, 14 Feb 2025 13:03:46 -0500, "Edward Rawde"
<invalid@invalid.invalid> wrote:
"Bill Sloman" <bill.sloman@ieee.org> wrote in message news:vompa5$3bjpm$1@dont-email.me...
On 14/02/2025 5:24 am, Edward Rawde wrote:
"Bill Sloman" <bill.sloman@ieee.org> wrote in message news:vol49p$2vd0d$1@dont-email.me...
On 14/02/2025 1:45 am, Edward Rawde wrote:
"Bill Sloman" <bill.sloman@ieee.org> wrote in message news:voh7a5$26aqj$1@dont-email.me...
On 10/02/2025 5:18 pm, Bill Sloman wrote:After fixing line wraps I had to move U1 down into position.
Basically same idea, but two separate controllable asymmetric current mirrors, rather than one, and no current steering.
The
half-wave rectifier still seems to be the source of the distortion in the stabilised output.
C25 and C26 take out as much of it as I can. Increasing them - from 15nF to 33nF makes the distortion worse. Splitting the
resistors into three rather than two and adding two more capacitors might help, but what this circuit needs is more
insight,
rather than more components.
Splitting the resistors did help, and the optimum capacitor value at C25, C26, C27 and C28 turned out to be 4.7nF. The
second
and
fifth harmonics were just 80dB below the fundamental and the third 91dB down. Not dramatically good, but respectable.
Other changes were less successful - the current mirror approach does suffer from the need to split the waveform in order to
generate the amplitude correction waveform and minimising the 2usec wide switching spikes that show up at cross-over is what
it
takes to get it to work tolerably well
I've swapped out the LT1115 for the LT1678 - that doesn't seem to suffer from parasitic oscillations in LTSpice 24, so it
should
simulate tolerably fast.
I then noticed an issue with C10 so I converted to ANSI in Notepad++ and saved the file.
When I picked up your text file, I noted that C10 (on the output of U4, the LTC6655-1.25 voltage reference) had gone back to
3.3 -
no suffix. I set it back to 3300n(F) and the circuit worked as it did for me with the harmonics mostly 80dB down with the
third
harmonic about 91dB down
Simulation then failed without giving any clue what was wrong.
But instead of spending hours tracing the problem I removed .ENDS from the BAS70 model.
I put it back in again. and it didn't make any difference to my simulation.
It will for anyone else using 24.1.2.
I note that the model for MMBF4391 is still present and does not have .ENDS so why should BAS70 need it?
In 24.1.2 you get errors which make no sense and do not mention BAS70.
The BAS70 model dates back to 2015. It's a classic Spice model - and LTSpice is supposed to run them.
Online searching finds "A SPICE model starts with a .SUBCKT statement and ends with an .ENDS statement" which does not seem to be
applicable here.
24.1.2 seems to simulate just fine if .ENDS is removed from the BAS70 model. >>But if .ENDS is included then the simulation does not run and the following log is produced.
Now tested on two different computers running 24.1.2
LTspice 24.1.2 for Windows
Circuit: C:\Users\Edward\Desktop\sloman 14 Feb 2025\sloman.net
Start Time: Fri Feb 14 11:10:46 2025
C:\Users\Edward\Desktop\sloman 14 Feb 2025\sloman.net(2): This sub-circuit name is not defined.
X§U1 N040 N035 N006 N052 N039 LT1360
^^^^^^^
C:\Users\Edward\Desktop\sloman 14 Feb 2025\sloman.net(22): This sub-circuit name is not defined.
X§U5 N037 N019 Vcc Vee N002 LT1056
^^^^^^^
C:\Users\Edward\Desktop\sloman 14 Feb 2025\sloman.net(25): This sub-circuit name is not defined.
X§U2 0 N033 N017 N051 N030 OP27
^^^^^
C:\Users\Edward\Desktop\sloman 14 Feb 2025\sloman.net(47): This sub-circuit name is not defined.
X§U4 N038 N038 0 N037 N037 LTC6655-1.25
^^^^^^^^^^^^^
C:\Users\Edward\Desktop\sloman 14 Feb 2025\sloman.net(57): This sub-circuit name is not defined.
X§U6 N032 N021 Vcc Vee filt1 LT1013
^^^^^^^
C:\Users\Edward\Desktop\sloman 14 Feb 2025\sloman.net(62): This sub-circuit name is not defined.
X§U7 N029 N013 Vcc Vee filter2 LT1013
^^^^^^^
C:\Users\Edward\Desktop\sloman 14 Feb 2025\sloman.net(80): This sub-circuit name is not defined.
X§U9 0 N025 Vcc Vee N034 LT1013
^^^^^^^
C:\Users\Edward\Desktop\sloman 14 Feb 2025\sloman.net(81): This sub-circuit name is not defined.
X§U10 0 N044 Vcc Vee N001 LT1056
^^^^^^^
C:\Users\Edward\Desktop\sloman 14 Feb 2025\sloman.net(87): This sub-circuit name is not defined.
X§U11 0 N022 Vcc Vee N023 LT1013
^^^^^^^
C:\Users\Edward\Desktop\sloman 14 Feb 2025\sloman.net(102): This sub-circuit name is not defined.
X§U3 0 N011 N024 N004 N045 LT1678
^^^^^^^
C:\Users\Edward\Desktop\sloman 14 Feb 2025\sloman.net(103): This sub-circuit name is not defined.
X§U8 0 N014 Vout N005 N046 LT1678
^^^^^^^
The ^^ characters are positioned under the device type.
Under LT1360 for the first error.
Formatting differences may not show this correctly.
It took me a while not long ago to slowly add/remove parts of your circuit until I found out that removing .ENDS in the BAS70
model
on the schematic eliminated the above issues and the simulation in 24.1.0 ran fine.
Simulation now runs fine at about 44 ms/s in LTSPice 24.1.2
FFT is approaching 60dB
Not having the right value capacitor at C10 usually totally messes it up. We've had that issue before.
C10 is 3.3uF
Changing to 3300n and resimulating makes no difference. Definitely only 60dB difference between 1kHz and 2,3,4,5kHz
Exact circuit I'm simulating (in 24.1.2) included below.
And when I run it (after having put U1 back where I intended it to go and restored it's connection to the negative rail) I got
the
second to the fifth harmonics harmonics 80dB below the fundamental with the third 91dB down. When I stretched the frequency
display out to 100kHz the higher harmonics were going down.
I ran your circuit to 10 seconds on 24.1.2 (about 4 minutes) and took a sample of about 60 cycles near 10 seconds.
I then did an FFT on Vout (U8 output) and selected current zoom extent and Blackman-Harris Window.
The vertical scale has 20dB at the top with 1kHz at 0dB one square down. >>Another three squares down are 2,3,4,5 kHz approaching the 60dB line.
So let's copy the asc file to another computer with LTSPice 17.0.34.0 and no component updates since installation.
Fix the position of U1 and add .ENDS to the BAS70 model. Simulate.
Speed is about the same 44ms/s but drops to 7ms/s after about 2 seconds simulated and then goes back to 44ms/s
Appearance is as above. 3.2V pk initial transient then settling at 1.6V pk. >>Same FFT as above.
Approaching 80dB at 2kHz, 3kHz 4kHz 75dB, 5kHz 65dB
Remove .ENDS from BAS70 model and resimulate.
Similar result depends a little on exact sample taken, maybe a little worse at 2kHz.
Put .ENDS back again and resimulate. Exactly the same FFT result so .ENDS as used here is best removed to avoid issues when
upgrading to 24.1.x
.ENDS is only an issue in 24.1.0 or later and only in the context described above.
So I wonder which simulation is closer to the truth.
I did let it settle down for two seconds before taking the FFT of V(out) onver the next second or so.
Simulated circuit included below.
I can get 80dB by adding an LC tuned circuit to a simple phase shift oscillator of the type which turns up here:
https://www.google.com/search?q=sine+wave+oscillator&udm=2
Where? There's a lot of stuff there.
Phase shift oscillator with feedback from the collector through CRCRCRCR to the base.
That is the simplest phase shift oscillator. Why didn't you identify it when you first mentioned it?
Because it didn't matter and there is more than one example of that type of circuit.
Most circuits which turn up there can't manage more than 60dB and those which can are unlikely to manage more than 90dB.
It's not long ago when I didn't think I'd do better than 90dB in simulation, but I kept at it. Now I can do 135dB in simulation
with
all simulated real (yes ok that's a contradiction) components.
No gain control yet but for unknown reasons it does run at constant (unpredictable) amplitude with very critical emitter
resistor
adjustment.
It's probably relying on the change in current gain with changing collector-base voltage. It is a small effect - the Early
effect - and non-linear.
I'm thinking of trying the sample/hold method posted by JM but with real components.
So I need to turn a FET on (not sure for how long yet) at the peaks of the sine wave.
Sample and holds tend to put spikes on the supply rails. Keeping them out of the output can take a lot of work.
Yeah I've had that problem before, decades ago.
A capacitively coupled inverted sampling signal was able to sufficiently remove the problem of the sampling signal appearing
in
the
output.
Reduce rather than remove. Cancellation schemes rarely work perfectly.
But that may not work at 140dB down.
Here is the exact version of your circuit from my most recent simulation of it.
Give or take the usual problems.
--
Bill Sloman, Sydney
.ends is only used to end a .subckt so ltspice is correct to warn
about it.
"Bill Sloman" <bill.sloman@ieee.org> wrote in message news:vompa5$3bjpm$1@dont-email.me......
On 14/02/2025 5:24 am, Edward Rawde wrote:
"Bill Sloman" <bill.sloman@ieee.org> wrote in message news:vol49p$2vd0d$1@dont-email.me...
On 14/02/2025 1:45 am, Edward Rawde wrote:
"Bill Sloman" <bill.sloman@ieee.org> wrote in message news:voh7a5$26aqj$1@dont-email.me...
On 10/02/2025 5:18 pm, Bill Sloman wrote:
On Mon, 10 Feb 2025 17:18:01 +1100, Bill Sloman <bill.sloman@ieee.org>
wrote:
Basically same idea, but two separate controllable asymmetric current
mirrors, rather than one, and no current steering. The half-wave
rectifier still seems to be the source of the distortion in the
stabilised output.
C25 and C26 take out as much of it as I can. Increasing them - from 15nF
to 33nF makes the distortion worse. Splitting the resistors into three
rather than two and adding two more capacitors might help, but what this
circuit needs is more insight, rather than more components.
What is the point of a push-pull current mirror?
You don't need response at dc.
A "class A" (for want of a better term) mirror with
minimal current deviation will have distortion levels orders of
magnitude less than the circuit you propose.
"JM" <sunaecoNoChoppedPork@gmail.com> wrote in message news:637vqjpics9oqi4gsv4vv200cf7t3kovb6@4ax.com...
On Fri, 14 Feb 2025 13:03:46 -0500, "Edward Rawde"
<invalid@invalid.invalid> wrote:
"Bill Sloman" <bill.sloman@ieee.org> wrote in message news:vompa5$3bjpm$1@dont-email.me...
On 14/02/2025 5:24 am, Edward Rawde wrote:
"Bill Sloman" <bill.sloman@ieee.org> wrote in message news:vol49p$2vd0d$1@dont-email.me...The BAS70 model dates back to 2015. It's a classic Spice model - and LTSpice is supposed to run them.
On 14/02/2025 1:45 am, Edward Rawde wrote:
"Bill Sloman" <bill.sloman@ieee.org> wrote in message news:voh7a5$26aqj$1@dont-email.me...
On 10/02/2025 5:18 pm, Bill Sloman wrote:After fixing line wraps I had to move U1 down into position.
Basically same idea, but two separate controllable asymmetric current mirrors, rather than one, and no current steering.
The
half-wave rectifier still seems to be the source of the distortion in the stabilised output.
C25 and C26 take out as much of it as I can. Increasing them - from 15nF to 33nF makes the distortion worse. Splitting the
resistors into three rather than two and adding two more capacitors might help, but what this circuit needs is more
insight,
rather than more components.
Splitting the resistors did help, and the optimum capacitor value at C25, C26, C27 and C28 turned out to be 4.7nF. The
second
and
fifth harmonics were just 80dB below the fundamental and the third 91dB down. Not dramatically good, but respectable.
Other changes were less successful - the current mirror approach does suffer from the need to split the waveform in order to
generate the amplitude correction waveform and minimising the 2usec wide switching spikes that show up at cross-over is what
it
takes to get it to work tolerably well
I've swapped out the LT1115 for the LT1678 - that doesn't seem to suffer from parasitic oscillations in LTSpice 24, so it
should
simulate tolerably fast.
I then noticed an issue with C10 so I converted to ANSI in Notepad++ and saved the file.
When I picked up your text file, I noted that C10 (on the output of U4, the LTC6655-1.25 voltage reference) had gone back to
3.3 -
no suffix. I set it back to 3300n(F) and the circuit worked as it did for me with the harmonics mostly 80dB down with the
third
harmonic about 91dB down
Simulation then failed without giving any clue what was wrong.
But instead of spending hours tracing the problem I removed .ENDS from the BAS70 model.
I put it back in again. and it didn't make any difference to my simulation.
It will for anyone else using 24.1.2.
I note that the model for MMBF4391 is still present and does not have .ENDS so why should BAS70 need it?
In 24.1.2 you get errors which make no sense and do not mention BAS70. >>>>
Online searching finds "A SPICE model starts with a .SUBCKT statement and ends with an .ENDS statement" which does not seem to be
applicable here.
24.1.2 seems to simulate just fine if .ENDS is removed from the BAS70 model.
But if .ENDS is included then the simulation does not run and the following log is produced.
Now tested on two different computers running 24.1.2
LTspice 24.1.2 for Windows
Circuit: C:\Users\Edward\Desktop\sloman 14 Feb 2025\sloman.net
Start Time: Fri Feb 14 11:10:46 2025
C:\Users\Edward\Desktop\sloman 14 Feb 2025\sloman.net(2): This sub-circuit name is not defined.
X§U1 N040 N035 N006 N052 N039 LT1360
^^^^^^^
C:\Users\Edward\Desktop\sloman 14 Feb 2025\sloman.net(22): This sub-circuit name is not defined.
X§U5 N037 N019 Vcc Vee N002 LT1056
^^^^^^^
C:\Users\Edward\Desktop\sloman 14 Feb 2025\sloman.net(25): This sub-circuit name is not defined.
X§U2 0 N033 N017 N051 N030 OP27
^^^^^
C:\Users\Edward\Desktop\sloman 14 Feb 2025\sloman.net(47): This sub-circuit name is not defined.
X§U4 N038 N038 0 N037 N037 LTC6655-1.25
^^^^^^^^^^^^^
C:\Users\Edward\Desktop\sloman 14 Feb 2025\sloman.net(57): This sub-circuit name is not defined.
X§U6 N032 N021 Vcc Vee filt1 LT1013
^^^^^^^
C:\Users\Edward\Desktop\sloman 14 Feb 2025\sloman.net(62): This sub-circuit name is not defined.
X§U7 N029 N013 Vcc Vee filter2 LT1013
^^^^^^^
C:\Users\Edward\Desktop\sloman 14 Feb 2025\sloman.net(80): This sub-circuit name is not defined.
X§U9 0 N025 Vcc Vee N034 LT1013
^^^^^^^
C:\Users\Edward\Desktop\sloman 14 Feb 2025\sloman.net(81): This sub-circuit name is not defined.
X§U10 0 N044 Vcc Vee N001 LT1056
^^^^^^^
C:\Users\Edward\Desktop\sloman 14 Feb 2025\sloman.net(87): This sub-circuit name is not defined.
X§U11 0 N022 Vcc Vee N023 LT1013
^^^^^^^
C:\Users\Edward\Desktop\sloman 14 Feb 2025\sloman.net(102): This sub-circuit name is not defined.
X§U3 0 N011 N024 N004 N045 LT1678
^^^^^^^
C:\Users\Edward\Desktop\sloman 14 Feb 2025\sloman.net(103): This sub-circuit name is not defined.
X§U8 0 N014 Vout N005 N046 LT1678
^^^^^^^
The ^^ characters are positioned under the device type.
Under LT1360 for the first error.
Formatting differences may not show this correctly.
It took me a while not long ago to slowly add/remove parts of your circuit until I found out that removing .ENDS in the BAS70
model
on the schematic eliminated the above issues and the simulation in 24.1.0 ran fine.
Simulation now runs fine at about 44 ms/s in LTSPice 24.1.2
FFT is approaching 60dB
Not having the right value capacitor at C10 usually totally messes it up. We've had that issue before.
C10 is 3.3uF
Changing to 3300n and resimulating makes no difference. Definitely only 60dB difference between 1kHz and 2,3,4,5kHz
Exact circuit I'm simulating (in 24.1.2) included below.
And when I run it (after having put U1 back where I intended it to go and restored it's connection to the negative rail) I got
the
second to the fifth harmonics harmonics 80dB below the fundamental with the third 91dB down. When I stretched the frequency
display out to 100kHz the higher harmonics were going down.
I ran your circuit to 10 seconds on 24.1.2 (about 4 minutes) and took a sample of about 60 cycles near 10 seconds.
I then did an FFT on Vout (U8 output) and selected current zoom extent and Blackman-Harris Window.
The vertical scale has 20dB at the top with 1kHz at 0dB one square down. >>> Another three squares down are 2,3,4,5 kHz approaching the 60dB line.
So let's copy the asc file to another computer with LTSPice 17.0.34.0 and no component updates since installation.
Fix the position of U1 and add .ENDS to the BAS70 model. Simulate.
Speed is about the same 44ms/s but drops to 7ms/s after about 2 seconds simulated and then goes back to 44ms/s
Appearance is as above. 3.2V pk initial transient then settling at 1.6V pk. >>> Same FFT as above.
Approaching 80dB at 2kHz, 3kHz 4kHz 75dB, 5kHz 65dB
Remove .ENDS from BAS70 model and resimulate.
Similar result depends a little on exact sample taken, maybe a little worse at 2kHz.
Put .ENDS back again and resimulate. Exactly the same FFT result so .ENDS as used here is best removed to avoid issues when
upgrading to 24.1.x
.ENDS is only an issue in 24.1.0 or later and only in the context described above.
So I wonder which simulation is closer to the truth.
I did let it settle down for two seconds before taking the FFT of V(out) onver the next second or so.
Simulated circuit included below.
I can get 80dB by adding an LC tuned circuit to a simple phase shift oscillator of the type which turns up here:
https://www.google.com/search?q=sine+wave+oscillator&udm=2
Where? There's a lot of stuff there.
Phase shift oscillator with feedback from the collector through CRCRCRCR to the base.
That is the simplest phase shift oscillator. Why didn't you identify it when you first mentioned it?
Because it didn't matter and there is more than one example of that type of circuit.
Most circuits which turn up there can't manage more than 60dB and those which can are unlikely to manage more than 90dB.
It's not long ago when I didn't think I'd do better than 90dB in simulation, but I kept at it. Now I can do 135dB in simulation
with
all simulated real (yes ok that's a contradiction) components.
No gain control yet but for unknown reasons it does run at constant (unpredictable) amplitude with very critical emitter
resistor
adjustment.
It's probably relying on the change in current gain with changing collector-base voltage. It is a small effect - the Early
effect - and non-linear.
I'm thinking of trying the sample/hold method posted by JM but with real components.
So I need to turn a FET on (not sure for how long yet) at the peaks of the sine wave.
Sample and holds tend to put spikes on the supply rails. Keeping them out of the output can take a lot of work.
Yeah I've had that problem before, decades ago.
A capacitively coupled inverted sampling signal was able to sufficiently remove the problem of the sampling signal appearing
in
the
output.
Reduce rather than remove. Cancellation schemes rarely work perfectly. >>>>
But that may not work at 140dB down.
Here is the exact version of your circuit from my most recent simulation of it.
Give or take the usual problems.
--
Bill Sloman, Sydney
.ends is only used to end a .subckt so ltspice is correct to warn
about it.
Yes I came to that conclusion a few minutes ago.
In versions prior to 24.1.0 .ENDS appears to be ignored when used without .SUBCKT
But In 24.1.0 or later the use of .ENDS without .SUBCKT can cause a simulation to fail with warnings which are not helpful when
tracing the cause of the problem.
On Mon, 10 Feb 2025 17:18:01 +1100, Bill Sloman <bill.sloman@ieee.org>
wrote:
Basically same idea, but two separate controllable asymmetric current >>mirrors, rather than one, and no current steering. The half-wave
rectifier still seems to be the source of the distortion in the
stabilised output.
C25 and C26 take out as much of it as I can. Increasing them - from 15nF
to 33nF makes the distortion worse. Splitting the resistors into three >>rather than two and adding two more capacitors might help, but what this >>circuit needs is more insight, rather than more components.
What is the point of a push-pull current mirror? You don't need
response at dc. A "class A" (for want of a better term) mirror with
minimal current deviation will have distortion levels orders of
magnitude less than the circuit you propose.
"JM" <sunaecoNoChoppedPork@gmail.com> wrote in message news:gp6vqjl5oma32tga136kspreh7a8182ofg@4ax.com...
On Mon, 10 Feb 2025 17:18:01 +1100, Bill Sloman <bill.sloman@ieee.org>
wrote:
Basically same idea, but two separate controllable asymmetric current
mirrors, rather than one, and no current steering. The half-wave
rectifier still seems to be the source of the distortion in the
stabilised output.
C25 and C26 take out as much of it as I can. Increasing them - from 15nF >>> to 33nF makes the distortion worse. Splitting the resistors into three
rather than two and adding two more capacitors might help, but what this >>> circuit needs is more insight, rather than more components.
What is the point of a push-pull current mirror? You don't need
response at dc. A "class A" (for want of a better term) mirror with
minimal current deviation will have distortion levels orders of
magnitude less than the circuit you propose.
Is there any specific reason for the npn Q5?
Replacing it and R25 with a single 100k resistor from U2 to Q1 base seems to work just as well.
2kHz is 141dB down measured with cursors on a zoomed in FFT in LTSPice 24.1.2
On 15/02/2025 6:41 am, JM wrote:
On Mon, 10 Feb 2025 17:18:01 +1100, Bill Sloman <bill.sloman@ieee.org>
wrote:
Basically same idea, but two separate controllable asymmetric current
mirrors, rather than one, and no current steering. The half-wave
rectifier still seems to be the source of the distortion in the
stabilised output.
C25 and C26 take out as much of it as I can. Increasing them - from 15nF >>> to 33nF makes the distortion worse. Splitting the resistors into three
rather than two and adding two more capacitors might help, but what this >>> circuit needs is more insight, rather than more components.
What is the point of a push-pull current mirror?
It starts up faster.
You don't need response at dc.
But you do have to wait a while for blocking capacitors to charge up.
On 16/02/2025 2:18 pm, Edward Rawde wrote:
"JM" <sunaecoNoChoppedPork@gmail.com> wrote in message news:gp6vqjl5oma32tga136kspreh7a8182ofg@4ax.com...
On Mon, 10 Feb 2025 17:18:01 +1100, Bill Sloman <bill.sloman@ieee.org>
wrote:
Basically same idea, but two separate controllable asymmetric current
mirrors, rather than one, and no current steering. The half-wave
rectifier still seems to be the source of the distortion in the
stabilised output.
C25 and C26 take out as much of it as I can. Increasing them - from 15nF >>>> to 33nF makes the distortion worse. Splitting the resistors into three >>>> rather than two and adding two more capacitors might help, but what this >>>> circuit needs is more insight, rather than more components.
What is the point of a push-pull current mirror? You don't need
response at dc. A "class A" (for want of a better term) mirror with
minimal current deviation will have distortion levels orders of
magnitude less than the circuit you propose.
Is there any specific reason for the npn Q5?
Replacing it and R25 with a single 100k resistor from U2 to Q1 base seems to work just as well.
2kHz is 141dB down measured with cursors on a zoomed in FFT in LTSPice 24.1.2
Complementary pairs often work better than simple emitter followers.
John May probably has a good reason for the choice. I've used them from time to time.
https://en.wikipedia.org/wiki/Sziklai_pair
--
Bill Sloman, Sydney
"Bill Sloman" <bill.sloman@ieee.org> wrote in message news:vorsg8$emeo$7@dont-email.me...
On 16/02/2025 2:18 pm, Edward Rawde wrote:
"JM" <sunaecoNoChoppedPork@gmail.com> wrote in message news:gp6vqjl5oma32tga136kspreh7a8182ofg@4ax.com...
On Mon, 10 Feb 2025 17:18:01 +1100, Bill Sloman <bill.sloman@ieee.org> >>>> wrote:
Basically same idea, but two separate controllable asymmetric current >>>>> mirrors, rather than one, and no current steering. The half-wave
rectifier still seems to be the source of the distortion in the
stabilised output.
C25 and C26 take out as much of it as I can. Increasing them - from 15nF >>>>> to 33nF makes the distortion worse. Splitting the resistors into three >>>>> rather than two and adding two more capacitors might help, but what this >>>>> circuit needs is more insight, rather than more components.
What is the point of a push-pull current mirror? You don't need
response at dc. A "class A" (for want of a better term) mirror with
minimal current deviation will have distortion levels orders of
magnitude less than the circuit you propose.
Is there any specific reason for the npn Q5?
Replacing it and R25 with a single 100k resistor from U2 to Q1 base seems to work just as well.
2kHz is 141dB down measured with cursors on a zoomed in FFT in LTSPice 24.1.2
Complementary pairs often work better than simple emitter followers.
But it's not a Sziklai pair. Both base-emiiter currents flow through R25
The Sziklai pair has been used for centuries.
There's one on page 566 (Pdf page 16) https://www.worldradiohistory.com/UK/Wireless-World/60s/Wireless-World-1961-11.pdf
John May probably has a good reason for the choice. I've used them from time to time.
https://en.wikipedia.org/wiki/Sziklai_pair
On 17/02/2025 2:14 am, Edward Rawde wrote:
"Bill Sloman" <bill.sloman@ieee.org> wrote in message news:vorsg8$emeo$7@dont-email.me...
On 16/02/2025 2:18 pm, Edward Rawde wrote:
"JM" <sunaecoNoChoppedPork@gmail.com> wrote in message news:gp6vqjl5oma32tga136kspreh7a8182ofg@4ax.com...
On Mon, 10 Feb 2025 17:18:01 +1100, Bill Sloman <bill.sloman@ieee.org> >>>>> wrote:
Basically same idea, but two separate controllable asymmetric current >>>>>> mirrors, rather than one, and no current steering. The half-wave
rectifier still seems to be the source of the distortion in the
stabilised output.
C25 and C26 take out as much of it as I can. Increasing them - from 15nF >>>>>> to 33nF makes the distortion worse. Splitting the resistors into three >>>>>> rather than two and adding two more capacitors might help, but what this >>>>>> circuit needs is more insight, rather than more components.
What is the point of a push-pull current mirror? You don't need
response at dc. A "class A" (for want of a better term) mirror with >>>>> minimal current deviation will have distortion levels orders of
magnitude less than the circuit you propose.
Is there any specific reason for the npn Q5?
Replacing it and R25 with a single 100k resistor from U2 to Q1 base seems to work just as well.
2kHz is 141dB down measured with cursors on a zoomed in FFT in LTSPice 24.1.2
Complementary pairs often work better than simple emitter followers.
But it's not a Sziklai pair. Both base-emiiter currents flow through R25
It's still exploiting the same idea.
The Sziklai pair has been used for centuries.
The Wikipedia page lists a 1957 patent. Transistors had been around for perhaps ten years by then. I got into electronics around
1966 (as a graduate student in chemistry) and knew about complementary Darlington pairs from early on, though nobody called them
Sziklai pairs back then.
There's one on page 566 (Pdf page 16)
https://www.worldradiohistory.com/UK/Wireless-World/60s/Wireless-World-1961-11.pdf
John May probably has a good reason for the choice. I've used them from time to time.
https://en.wikipedia.org/wiki/Sziklai_pair
John May's post makes it clear that he didn't have a good reason to go for that arrangement - it was cut and pasted from from a
earlier circuit where it did make more sense. He also make it clear that your modification wasn't well thought out - the 100k
resistor isn't required at all, and would degrade the performance of the circuit (though not enough for anybody to notice).
--
Bill Sloman, Sydney
"Bill Sloman" <bill.sloman@ieee.org> wrote in message news:voualf$rm6g$8@dont-email.me...
On 17/02/2025 2:14 am, Edward Rawde wrote:
"Bill Sloman" <bill.sloman@ieee.org> wrote in message news:vorsg8$emeo$7@dont-email.me...
On 16/02/2025 2:18 pm, Edward Rawde wrote:
"JM" <sunaecoNoChoppedPork@gmail.com> wrote in message news:gp6vqjl5oma32tga136kspreh7a8182ofg@4ax.com...
On Mon, 10 Feb 2025 17:18:01 +1100, Bill Sloman <bill.sloman@ieee.org> >>>>>> wrote:
Basically same idea, but two separate controllable asymmetric current >>>>>>> mirrors, rather than one, and no current steering. The half-wave >>>>>>> rectifier still seems to be the source of the distortion in the
stabilised output.
C25 and C26 take out as much of it as I can. Increasing them - from 15nF
to 33nF makes the distortion worse. Splitting the resistors into three >>>>>>> rather than two and adding two more capacitors might help, but what this
circuit needs is more insight, rather than more components.
What is the point of a push-pull current mirror? You don't need
response at dc. A "class A" (for want of a better term) mirror with >>>>>> minimal current deviation will have distortion levels orders of
magnitude less than the circuit you propose.
Is there any specific reason for the npn Q5?
Replacing it and R25 with a single 100k resistor from U2 to Q1 base seems to work just as well.
2kHz is 141dB down measured with cursors on a zoomed in FFT in LTSPice 24.1.2
Complementary pairs often work better than simple emitter followers.
But it's not a Sziklai pair. Both base-emiiter currents flow through R25
It's still exploiting the same idea.
The Sziklai pair has been used for centuries.
The Wikipedia page lists a 1957 patent. Transistors had been around for perhaps ten years by then. I got into electronics around
1966 (as a graduate student in chemistry) and knew about complementary Darlington pairs from early on, though nobody called them
Sziklai pairs back then.
There's one on page 566 (Pdf page 16)
https://www.worldradiohistory.com/UK/Wireless-World/60s/Wireless-World-1961-11.pdf
John May probably has a good reason for the choice. I've used them from time to time.
https://en.wikipedia.org/wiki/Sziklai_pair
John May's post makes it clear that he didn't have a good reason to go for that arrangement - it was cut and pasted from from a
earlier circuit where it did make more sense. He also make it clear that your modification wasn't well thought out - the 100k
resistor isn't required at all, and would degrade the performance of the circuit (though not enough for anybody to notice).
Bill. The current in the resistor is about 500 nA.
Why would the resistor degrade the performance?
On 17/02/2025 3:53 pm, Edward Rawde wrote:
"Bill Sloman" <bill.sloman@ieee.org> wrote in message news:voualf$rm6g$8@dont-email.me...
On 17/02/2025 2:14 am, Edward Rawde wrote:
"Bill Sloman" <bill.sloman@ieee.org> wrote in message news:vorsg8$emeo$7@dont-email.me...It's still exploiting the same idea.
On 16/02/2025 2:18 pm, Edward Rawde wrote:
"JM" <sunaecoNoChoppedPork@gmail.com> wrote in message news:gp6vqjl5oma32tga136kspreh7a8182ofg@4ax.com...
On Mon, 10 Feb 2025 17:18:01 +1100, Bill Sloman <bill.sloman@ieee.org> >>>>>>> wrote:
Basically same idea, but two separate controllable asymmetric current >>>>>>>> mirrors, rather than one, and no current steering. The half-wave >>>>>>>> rectifier still seems to be the source of the distortion in the >>>>>>>> stabilised output.
C25 and C26 take out as much of it as I can. Increasing them - from 15nF
to 33nF makes the distortion worse. Splitting the resistors into three >>>>>>>> rather than two and adding two more capacitors might help, but what this
circuit needs is more insight, rather than more components.
What is the point of a push-pull current mirror? You don't need >>>>>>> response at dc. A "class A" (for want of a better term) mirror with >>>>>>> minimal current deviation will have distortion levels orders of
magnitude less than the circuit you propose.
Is there any specific reason for the npn Q5?
Replacing it and R25 with a single 100k resistor from U2 to Q1 base seems to work just as well.
2kHz is 141dB down measured with cursors on a zoomed in FFT in LTSPice 24.1.2
Complementary pairs often work better than simple emitter followers.
But it's not a Sziklai pair. Both base-emiiter currents flow through R25 >>>
The Sziklai pair has been used for centuries.
The Wikipedia page lists a 1957 patent. Transistors had been around for perhaps ten years by then. I got into electronics around
1966 (as a graduate student in chemistry) and knew about complementary Darlington pairs from early on, though nobody called them
Sziklai pairs back then.
There's one on page 566 (Pdf page 16)
https://www.worldradiohistory.com/UK/Wireless-World/60s/Wireless-World-1961-11.pdf
John May probably has a good reason for the choice. I've used them from time to time.
https://en.wikipedia.org/wiki/Sziklai_pair
John May's post makes it clear that he didn't have a good reason to go for that arrangement - it was cut and pasted from from a
earlier circuit where it did make more sense. He also make it clear that your modification wasn't well thought out - the 100k
resistor isn't required at all, and would degrade the performance of the circuit (though not enough for anybody to notice).
Bill. The current in the resistor is about 500 nA.
Why would the resistor degrade the performance?
The 2N38906 has 10pF of input capacitance and 4.5pF of output capacitance. The resistor introduces about 1usec of lag, which
degrades the high frequency performance.
In a 1kHz oscillator this isn't going to worry anybody,
and the LT1013 is slow enough that it won't matter - C9 kills any risk there - but the resistor clearly isn't doing anything
useful, so one has to wonder why you bothered to add it.
--
Bill Sloman, Sydney
"Bill Sloman" <bill.sloman@ieee.org> wrote in message news:voujeq$11678$2@dont-email.me...
On 17/02/2025 3:53 pm, Edward Rawde wrote:
"Bill Sloman" <bill.sloman@ieee.org> wrote in message news:voualf$rm6g$8@dont-email.me...
On 17/02/2025 2:14 am, Edward Rawde wrote:
"Bill Sloman" <bill.sloman@ieee.org> wrote in message news:vorsg8$emeo$7@dont-email.me...It's still exploiting the same idea.
On 16/02/2025 2:18 pm, Edward Rawde wrote:But it's not a Sziklai pair. Both base-emiiter currents flow through R25 >>>>
"JM" <sunaecoNoChoppedPork@gmail.com> wrote in message news:gp6vqjl5oma32tga136kspreh7a8182ofg@4ax.com...
On Mon, 10 Feb 2025 17:18:01 +1100, Bill Sloman <bill.sloman@ieee.org> >>>>>>>> wrote:
Basically same idea, but two separate controllable asymmetric current >>>>>>>>> mirrors, rather than one, and no current steering. The half-wave >>>>>>>>> rectifier still seems to be the source of the distortion in the >>>>>>>>> stabilised output.
C25 and C26 take out as much of it as I can. Increasing them - from 15nF
to 33nF makes the distortion worse. Splitting the resistors into three
rather than two and adding two more capacitors might help, but what this
circuit needs is more insight, rather than more components.
What is the point of a push-pull current mirror? You don't need >>>>>>>> response at dc. A "class A" (for want of a better term) mirror with >>>>>>>> minimal current deviation will have distortion levels orders of >>>>>>>> magnitude less than the circuit you propose.
Is there any specific reason for the npn Q5?
Replacing it and R25 with a single 100k resistor from U2 to Q1 base seems to work just as well.
2kHz is 141dB down measured with cursors on a zoomed in FFT in LTSPice 24.1.2
Complementary pairs often work better than simple emitter followers. >>>>>
The Sziklai pair has been used for centuries.
The Wikipedia page lists a 1957 patent. Transistors had been around for perhaps ten years by then. I got into electronics around
1966 (as a graduate student in chemistry) and knew about complementary Darlington pairs from early on, though nobody called them
Sziklai pairs back then.
There's one on page 566 (Pdf page 16)
https://www.worldradiohistory.com/UK/Wireless-World/60s/Wireless-World-1961-11.pdf
John May probably has a good reason for the choice. I've used them from time to time.
https://en.wikipedia.org/wiki/Sziklai_pair
John May's post makes it clear that he didn't have a good reason to go for that arrangement - it was cut and pasted from from a
earlier circuit where it did make more sense. He also make it clear that your modification wasn't well thought out - the 100k
resistor isn't required at all, and would degrade the performance of the circuit (though not enough for anybody to notice).
Bill. The current in the resistor is about 500 nA.
Why would the resistor degrade the performance?
The 2N38906 has 10pF of input capacitance and 4.5pF of output capacitance. The resistor introduces about 1usec of lag, which
degrades the high frequency performance.
Which is irrelevant for this circuit.
In a 1kHz oscillator this isn't going to worry anybody,
So why bother pointing it out?
and the LT1013 is slow enough that it won't matter - C9 kills any risk there - but the resistor clearly isn't doing anything
useful, so one has to wonder why you bothered to add it.
In any real circuit I would generally not connect a low impedance output from an op amp directly to the base of a transistor, but
this doesn't mean that there aren't cases where it's perfectly fine or desirable to do so.
In this case it doesn't matter, so why bother pointing out that it doesn't matter?
You can also argue that R7 isn't needed, but in any real circuit I would include both resistors.
I can always put 0 ohm in.
On 18/02/2025 3:54 am, Edward Rawde wrote:
"Bill Sloman" <bill.sloman@ieee.org> wrote in message news:voujeq$11678$2@dont-email.me...
On 17/02/2025 3:53 pm, Edward Rawde wrote:
"Bill Sloman" <bill.sloman@ieee.org> wrote in message news:voualf$rm6g$8@dont-email.me...
On 17/02/2025 2:14 am, Edward Rawde wrote:
"Bill Sloman" <bill.sloman@ieee.org> wrote in message news:vorsg8$emeo$7@dont-email.me...It's still exploiting the same idea.
On 16/02/2025 2:18 pm, Edward Rawde wrote:But it's not a Sziklai pair. Both base-emiiter currents flow through R25 >>>>>
"JM" <sunaecoNoChoppedPork@gmail.com> wrote in message news:gp6vqjl5oma32tga136kspreh7a8182ofg@4ax.com...
On Mon, 10 Feb 2025 17:18:01 +1100, Bill Sloman <bill.sloman@ieee.org>
wrote:
Basically same idea, but two separate controllable asymmetric currentWhat is the point of a push-pull current mirror? You don't need >>>>>>>>> response at dc. A "class A" (for want of a better term) mirror with >>>>>>>>> minimal current deviation will have distortion levels orders of >>>>>>>>> magnitude less than the circuit you propose.
mirrors, rather than one, and no current steering. The half-wave >>>>>>>>>> rectifier still seems to be the source of the distortion in the >>>>>>>>>> stabilised output.
C25 and C26 take out as much of it as I can. Increasing them - from 15nF
to 33nF makes the distortion worse. Splitting the resistors into three
rather than two and adding two more capacitors might help, but what this
circuit needs is more insight, rather than more components. >>>>>>>>>
Is there any specific reason for the npn Q5?
Replacing it and R25 with a single 100k resistor from U2 to Q1 base seems to work just as well.
2kHz is 141dB down measured with cursors on a zoomed in FFT in LTSPice 24.1.2
Complementary pairs often work better than simple emitter followers. >>>>>>
The Sziklai pair has been used for centuries.
The Wikipedia page lists a 1957 patent. Transistors had been around for perhaps ten years by then. I got into electronics
around
1966 (as a graduate student in chemistry) and knew about complementary Darlington pairs from early on, though nobody called
them
Sziklai pairs back then.
There's one on page 566 (Pdf page 16)
https://www.worldradiohistory.com/UK/Wireless-World/60s/Wireless-World-1961-11.pdf
John May probably has a good reason for the choice. I've used them from time to time.
https://en.wikipedia.org/wiki/Sziklai_pair
John May's post makes it clear that he didn't have a good reason to go for that arrangement - it was cut and pasted from from
a
earlier circuit where it did make more sense. He also make it clear that your modification wasn't well thought out - the 100k
resistor isn't required at all, and would degrade the performance of the circuit (though not enough for anybody to notice).
Bill. The current in the resistor is about 500 nA.
Why would the resistor degrade the performance?
The 2N38906 has 10pF of input capacitance and 4.5pF of output capacitance. The resistor introduces about 1usec of lag, which
degrades the high frequency performance.
Which is irrelevant for this circuit.
In a 1kHz oscillator this isn't going to worry anybody,
So why bother pointing it out?
and the LT1013 is slow enough that it won't matter - C9 kills any risk there - but the resistor clearly isn't doing anything
useful, so one has to wonder why you bothered to add it.
That is the question that matters.
In any real circuit I would generally not connect a low impedance output from an op amp directly to the base of a transistor, but
this doesn't mean that there aren't cases where it's perfectly fine or desirable to do so.
In this case it doesn't matter, so why bother pointing out that it doesn't matter?
You've been complaining that my circuits include too many components, even though each one of the serves a purpose.
You should expect me to complain when one of your circuits includes a useless component which degrades it's performance even it it
is only a very minor degradation.
You can also argue that R7 isn't needed, but in any real circuit I would include both resistors.
I can always put 0 ohm in.
I automatically put a resistor in series with the gate of a power MOSFET.
Only some of them need it to kill high-frequency oscillation with the parts originally selected, but purchasing does like to swap
in cheaper parts over the life of a product. This isn't a parallel situation.
--
Bill Sloman, Sydney
"Bill Sloman" <bill.sloman@ieee.org> wrote in message news:vp0svp$1d8re$6@dont-email.me...
On 18/02/2025 3:54 am, Edward Rawde wrote:
"Bill Sloman" <bill.sloman@ieee.org> wrote in message news:voujeq$11678$2@dont-email.me...
On 17/02/2025 3:53 pm, Edward Rawde wrote:
"Bill Sloman" <bill.sloman@ieee.org> wrote in message news:voualf$rm6g$8@dont-email.me...
On 17/02/2025 2:14 am, Edward Rawde wrote:
"Bill Sloman" <bill.sloman@ieee.org> wrote in message news:vorsg8$emeo$7@dont-email.me...
On 16/02/2025 2:18 pm, Edward Rawde wrote:But it's not a Sziklai pair. Both base-emiiter currents flow through R25
"JM" <sunaecoNoChoppedPork@gmail.com> wrote in message news:gp6vqjl5oma32tga136kspreh7a8182ofg@4ax.com...
On Mon, 10 Feb 2025 17:18:01 +1100, Bill Sloman <bill.sloman@ieee.org>
wrote:
Basically same idea, but two separate controllable asymmetric currentWhat is the point of a push-pull current mirror? You don't need >>>>>>>>>> response at dc. A "class A" (for want of a better term) mirror with >>>>>>>>>> minimal current deviation will have distortion levels orders of >>>>>>>>>> magnitude less than the circuit you propose.
mirrors, rather than one, and no current steering. The half-wave >>>>>>>>>>> rectifier still seems to be the source of the distortion in the >>>>>>>>>>> stabilised output.
C25 and C26 take out as much of it as I can. Increasing them - from 15nF
to 33nF makes the distortion worse. Splitting the resistors into three
rather than two and adding two more capacitors might help, but what this
circuit needs is more insight, rather than more components. >>>>>>>>>>
Is there any specific reason for the npn Q5?
Replacing it and R25 with a single 100k resistor from U2 to Q1 base seems to work just as well.
2kHz is 141dB down measured with cursors on a zoomed in FFT in LTSPice 24.1.2
Complementary pairs often work better than simple emitter followers. >>>>>>>
It's still exploiting the same idea.
The Sziklai pair has been used for centuries.
The Wikipedia page lists a 1957 patent. Transistors had been around for perhaps ten years by then. I got into electronics
around
1966 (as a graduate student in chemistry) and knew about complementary Darlington pairs from early on, though nobody called
them
Sziklai pairs back then.
There's one on page 566 (Pdf page 16)
https://www.worldradiohistory.com/UK/Wireless-World/60s/Wireless-World-1961-11.pdf
John May probably has a good reason for the choice. I've used them from time to time.
https://en.wikipedia.org/wiki/Sziklai_pair
John May's post makes it clear that he didn't have a good reason to go for that arrangement - it was cut and pasted from from
a
earlier circuit where it did make more sense. He also make it clear that your modification wasn't well thought out - the 100k
resistor isn't required at all, and would degrade the performance of the circuit (though not enough for anybody to notice).
Bill. The current in the resistor is about 500 nA.
Why would the resistor degrade the performance?
The 2N38906 has 10pF of input capacitance and 4.5pF of output capacitance. The resistor introduces about 1usec of lag, which
degrades the high frequency performance.
Which is irrelevant for this circuit.
In a 1kHz oscillator this isn't going to worry anybody,
So why bother pointing it out?
and the LT1013 is slow enough that it won't matter - C9 kills any risk there - but the resistor clearly isn't doing anything
useful, so one has to wonder why you bothered to add it.
That is the question that matters.
But it doesn't matter to anyone else Bill.
In any real circuit I would generally not connect a low impedance output from an op amp directly to the base of a transistor, but
this doesn't mean that there aren't cases where it's perfectly fine or desirable to do so.
In this case it doesn't matter, so why bother pointing out that it doesn't matter?
You've been complaining that my circuits include too many components, even though each one of the serves a purpose.
So add another hundred ferrites and claim that each one serves a purpose if you want.
I don't mind.
You're still only going to get 60dB down in LTSpice 24.1.2
You should expect me to complain when one of your circuits includes a useless component which degrades it's performance even it it
is only a very minor degradation.
You can also argue that R7 isn't needed, but in any real circuit I would include both resistors.
I can always put 0 ohm in.
I automatically put a resistor in series with the gate of a power MOSFET.
I do too. Then I can put any value resistor in place from 0 ohm to infinity ohm.
Just like the resistor I put between U6 and Q1.
In any case this resistor doesn't actually exist. As resistors go it's about as real as Ceci n'est pas une pipe.
It only exists in the limited mathematical imagination of the computer in front of
So getting worked up over its exact value isn't very productive, don't you agree?
Only some of them need it to kill high-frequency oscillation with the parts originally selected, but purchasing does like to swap
in cheaper parts over the life of a product. This isn't a parallel situation.
On 18/02/2025 2:50 pm, Edward Rawde wrote:
"Bill Sloman" <bill.sloman@ieee.org> wrote in message news:vp0svp$1d8re$6@dont-email.me...
On 18/02/2025 3:54 am, Edward Rawde wrote:
"Bill Sloman" <bill.sloman@ieee.org> wrote in message news:voujeq$11678$2@dont-email.me...
On 17/02/2025 3:53 pm, Edward Rawde wrote:
"Bill Sloman" <bill.sloman@ieee.org> wrote in message news:voualf$rm6g$8@dont-email.me...
On 17/02/2025 2:14 am, Edward Rawde wrote:
"Bill Sloman" <bill.sloman@ieee.org> wrote in message news:vorsg8$emeo$7@dont-email.me...
On 16/02/2025 2:18 pm, Edward Rawde wrote:But it's not a Sziklai pair. Both base-emiiter currents flow through R25
"JM" <sunaecoNoChoppedPork@gmail.com> wrote in message news:gp6vqjl5oma32tga136kspreh7a8182ofg@4ax.com...
On Mon, 10 Feb 2025 17:18:01 +1100, Bill Sloman <bill.sloman@ieee.org>
wrote:
Basically same idea, but two separate controllable asymmetric currentWhat is the point of a push-pull current mirror? You don't need >>>>>>>>>>> response at dc. A "class A" (for want of a better term) mirror with
mirrors, rather than one, and no current steering. The half-wave >>>>>>>>>>>> rectifier still seems to be the source of the distortion in the >>>>>>>>>>>> stabilised output.
C25 and C26 take out as much of it as I can. Increasing them - from 15nF
to 33nF makes the distortion worse. Splitting the resistors into three
rather than two and adding two more capacitors might help, but what this
circuit needs is more insight, rather than more components. >>>>>>>>>>>
minimal current deviation will have distortion levels orders of >>>>>>>>>>> magnitude less than the circuit you propose.
Is there any specific reason for the npn Q5?
Replacing it and R25 with a single 100k resistor from U2 to Q1 base seems to work just as well.
2kHz is 141dB down measured with cursors on a zoomed in FFT in LTSPice 24.1.2
Complementary pairs often work better than simple emitter followers. >>>>>>>>
It's still exploiting the same idea.
The Sziklai pair has been used for centuries.
The Wikipedia page lists a 1957 patent. Transistors had been around for perhaps ten years by then. I got into electronics
around
1966 (as a graduate student in chemistry) and knew about complementary Darlington pairs from early on, though nobody called
them
Sziklai pairs back then.
There's one on page 566 (Pdf page 16)
https://www.worldradiohistory.com/UK/Wireless-World/60s/Wireless-World-1961-11.pdf
John May probably has a good reason for the choice. I've used them from time to time.
https://en.wikipedia.org/wiki/Sziklai_pair
John May's post makes it clear that he didn't have a good reason to go for that arrangement - it was cut and pasted from
from
a
earlier circuit where it did make more sense. He also make it clear that your modification wasn't well thought out - the
100k
resistor isn't required at all, and would degrade the performance of the circuit (though not enough for anybody to notice).
Bill. The current in the resistor is about 500 nA.
Why would the resistor degrade the performance?
The 2N38906 has 10pF of input capacitance and 4.5pF of output capacitance. The resistor introduces about 1usec of lag, which
degrades the high frequency performance.
Which is irrelevant for this circuit.
In a 1kHz oscillator this isn't going to worry anybody,
So why bother pointing it out?
and the LT1013 is slow enough that it won't matter - C9 kills any risk there - but the resistor clearly isn't doing anything
useful, so one has to wonder why you bothered to add it.
That is the question that matters.
But it doesn't matter to anyone else Bill.
What makes you think that? You may find it a comforting thought, but it strikes me a self-serving delusion.
In any real circuit I would generally not connect a low impedance output from an op amp directly to the base of a transistor,
but
this doesn't mean that there aren't cases where it's perfectly fine or desirable to do so.
In this case it doesn't matter, so why bother pointing out that it doesn't matter?
You've been complaining that my circuits include too many components, even though each one of the serves a purpose.
So add another hundred ferrites and claim that each one serves a purpose if you want.
I don't mind.
But you still complain about it.
The ferrites do serve a purpose, even if you can't see the point.
You're still only going to get 60dB down in LTSpice 24.1.2
So LTSpice 17 and LTSpice 24 give different results - not a good reason fro trusting either of them. If you want to make a fuss
about harmonic levels you have to measure them in a real circuit, which is expensive and time-consuming. John May has done it -
neither of us have.
You should expect me to complain when one of your circuits includes a useless component which degrades it's performance even itI do too. Then I can put any value resistor in place from 0 ohm to infinity ohm.
it
is only a very minor degradation.
You can also argue that R7 isn't needed, but in any real circuit I would include both resistors.
I can always put 0 ohm in.
I automatically put a resistor in series with the gate of a power MOSFET. >>
But the circuit won't work if the resistance is too high.
And production want to buying and fit a single resistor value.
Select on test resistors aren't popular - Cambridge Instruments used them from time to time, and production kept on proposing to
use a fixed resistor.
We were buying parts in six month chunks, and for that six months production always fitted the same resistor (and got bored). A
new batch of parts would need a different resistor.
Just like the resistor I put between U6 and Q1.
Far from it. You didn't know what it was doing, and didn't realise that you didn't need it.
In any case this resistor doesn't actually exist. As resistors go it's about as real as Ceci n'est pas une pipe.
It only exists in the limited mathematical imagination of the computer in front of
And it's cheaper and quicker to model a circuit that it is to build and test it. Within the limits of the model it's quite useful,
but the game to get to circuit that you can build, which is likely to work. No real circuit? No game.
So getting worked up over its exact value isn't very productive, don't you agree?
If you are silly enough to think like that this isn't going to be a productive discussion, and your part of it hasn't been for
quite a while.
Only some of them need it to kill high-frequency oscillation with the parts originally selected, but purchasing does like to
swap
in cheaper parts over the life of a product. This isn't a parallel situation.
--
Bill Sloman, Sydney
On 19/02/2025 5:40 am, Edward Rawde wrote:...
"Bill Sloman" <bill.sloman@ieee.org> wrote in message news:vp1acj$1j5t7$1@dont-email.me...
On 18/02/2025 2:50 pm, Edward Rawde wrote:
"Bill Sloman" <bill.sloman@ieee.org> wrote in message news:vp0svp$1d8re$6@dont-email.me...
On 18/02/2025 3:54 am, Edward Rawde wrote:
"Bill Sloman" <bill.sloman@ieee.org> wrote in message news:voujeq$11678$2@dont-email.me...
On 17/02/2025 3:53 pm, Edward Rawde wrote:
"Bill Sloman" <bill.sloman@ieee.org> wrote in message news:voualf$rm6g$8@dont-email.me...
On 17/02/2025 2:14 am, Edward Rawde wrote:
"Bill Sloman" <bill.sloman@ieee.org> wrote in message news:vorsg8$emeo$7@dont-email.me...
On 16/02/2025 2:18 pm, Edward Rawde wrote:
"JM" <sunaecoNoChoppedPork@gmail.com> wrote in message news:gp6vqjl5oma32tga136kspreh7a8182ofg@4ax.com...
On Mon, 10 Feb 2025 17:18:01 +1100, Bill Sloman <bill.sloman@ieee.org>
wrote:
Basically same idea, but two separate controllable asymmetric currentWhat is the point of a push-pull current mirror? You don't need >>>>>>>>>>>>> response at dc. A "class A" (for want of a better term) mirror with
mirrors, rather than one, and no current steering. The half-wave >>>>>>>>>>>>>> rectifier still seems to be the source of the distortion in the >>>>>>>>>>>>>> stabilised output.
C25 and C26 take out as much of it as I can. Increasing them - from 15nF
to 33nF makes the distortion worse. Splitting the resistors into three
rather than two and adding two more capacitors might help, but what this
circuit needs is more insight, rather than more components. >>>>>>>>>>>>>
minimal current deviation will have distortion levels orders of >>>>>>>>>>>>> magnitude less than the circuit you propose.
Is there any specific reason for the npn Q5?
Replacing it and R25 with a single 100k resistor from U2 to Q1 base seems to work just as well.
2kHz is 141dB down measured with cursors on a zoomed in FFT in LTSPice 24.1.2
Complementary pairs often work better than simple emitter followers.
But it's not a Sziklai pair. Both base-emiiter currents flow through R25
It's still exploiting the same idea.
The Sziklai pair has been used for centuries.
The Wikipedia page lists a 1957 patent. Transistors had been around for perhaps ten years by then. I got into electronics
around
1966 (as a graduate student in chemistry) and knew about complementary Darlington pairs from early on, though nobody
called
them
Sziklai pairs back then.
There's one on page 566 (Pdf page 16)
https://www.worldradiohistory.com/UK/Wireless-World/60s/Wireless-World-1961-11.pdf
John May probably has a good reason for the choice. I've used them from time to time.
https://en.wikipedia.org/wiki/Sziklai_pair
John May's post makes it clear that he didn't have a good reason to go for that arrangement - it was cut and pasted from
from
a
earlier circuit where it did make more sense. He also make it clear that your modification wasn't well thought out - the
100k
resistor isn't required at all, and would degrade the performance of the circuit (though not enough for anybody to
notice).
Bill. The current in the resistor is about 500 nA.
Why would the resistor degrade the performance?
The 2N38906 has 10pF of input capacitance and 4.5pF of output capacitance. The resistor introduces about 1usec of lag, which
degrades the high frequency performance.
Which is irrelevant for this circuit.
In a 1kHz oscillator this isn't going to worry anybody,
So why bother pointing it out?
and the LT1013 is slow enough that it won't matter - C9 kills any risk there - but the resistor clearly isn't doing anything
useful, so one has to wonder why you bothered to add it.
That is the question that matters.
But it doesn't matter to anyone else Bill.
What makes you think that? You may find it a comforting thought, but it strikes me a self-serving delusion.
It strikes me as an obvious fact.
I'm not expecting anyone else to offer any comment but it's interesting that they haven't.
And it's not like this group is only for the discussion of electronic matters, as the "Cracking Speech by JDV" thread shows.
You seem to be enjoying yourself there.
I think the circuit JM posted is likely to work.
Congratulations. You've said something sensible for once.
Two BCM61B devices would probably be fine for the current mirror.
A single LT1679 can be used for U1,5,6,8 with a cheaper device for the rest.
This is a less defensible observation.
U5,U6 and U8 are the phase shift oscillator. U1 should a cheap device that is part of the network that generates the amplitude
feedback signal fed into the integrator wrapped around U7 to generate the gain control signal that modulate the level of the
feedback sine wave that adjusts the output amplitude.
And C6 can be made from two polarized capacitors.
Sadly, you can't buy a pair of 940uF polarised capacitors. Two 1000uf polarised capacitors would be quite close enough
https://4donline.ihs.com/images/VipMasterIC/IC/VISH/VISH-S-A0010924709 /VISH-S-A0010924709-1.pdf?hkey=6D3A4C79FDBF58556ACFDE234799DDF0
are offered at +/-10% and +/-20% tolerance and 940uF is within 10% of 1000uF.
I(R17) runs at about 100uA and I(R21) runs at about 145uA -that is about 25mV across R17 and 36mV across R21. A single polarised
capacitor isn't going to get depolarised by 11mV of bias.
Putting 100uF polarised caps in parallel to R17 and R19 delivers harmonics about -135dB below the fundamental rather more cheaply,
and won't upset people who get nervous about polarised caps.
As we know, LTSpice isn't all that credible when it predicts very low harmonic content, so 470uF is perhaps a a bit much.
Q5, R25, R7 and C9 can be removed but keeping R7, C9 and a base series resistor for Q1 does no harm.
The simulation result in LTSpice 24.1.2 is the same, about -142dB at 2kHz. >>
Do you have any productive comments yourself?
So getting worked up over its exact value isn't very productive, don't you agree?
If you are silly enough to think like that this isn't going to be a productive discussion, and your part of it hasn't been for
quite a while.
Are you done coming across as a grumpy old headmaster talking to a student who didn't do their homework?
My approach to such a situation would be to offer the student help and encouragement.
That has been my approach, and it is what I mostly post. Some students don't notice that they are being offered help.
But it appears that yours would be along the lines of "You obviously don't know what you're doing you stupid kid" and "What you
should have done is..."
There's little point in being diplomatic with poor students.
Quite a few of them are resistant to the idea that they've got stuff wrong, and being diplomatic lets them skate around the
negative message.
I've have spelled this out quite explicitly from time to time over the twenty years I've been posting here.
<snip>
Bill Sloman, Sydney
"Bill Sloman" <bill.sloman@ieee.org> wrote in message news:vp1acj$1j5t7$1@dont-email.me...
On 18/02/2025 2:50 pm, Edward Rawde wrote:
"Bill Sloman" <bill.sloman@ieee.org> wrote in message news:vp0svp$1d8re$6@dont-email.me...
On 18/02/2025 3:54 am, Edward Rawde wrote:
"Bill Sloman" <bill.sloman@ieee.org> wrote in message news:voujeq$11678$2@dont-email.me...
On 17/02/2025 3:53 pm, Edward Rawde wrote:
"Bill Sloman" <bill.sloman@ieee.org> wrote in message news:voualf$rm6g$8@dont-email.me...
On 17/02/2025 2:14 am, Edward Rawde wrote:
"Bill Sloman" <bill.sloman@ieee.org> wrote in message news:vorsg8$emeo$7@dont-email.me...
On 16/02/2025 2:18 pm, Edward Rawde wrote:But it's not a Sziklai pair. Both base-emiiter currents flow through R25
"JM" <sunaecoNoChoppedPork@gmail.com> wrote in message news:gp6vqjl5oma32tga136kspreh7a8182ofg@4ax.com...
On Mon, 10 Feb 2025 17:18:01 +1100, Bill Sloman <bill.sloman@ieee.org>
wrote:
Basically same idea, but two separate controllable asymmetric currentWhat is the point of a push-pull current mirror? You don't need >>>>>>>>>>>> response at dc. A "class A" (for want of a better term) mirror with
mirrors, rather than one, and no current steering. The half-wave >>>>>>>>>>>>> rectifier still seems to be the source of the distortion in the >>>>>>>>>>>>> stabilised output.
C25 and C26 take out as much of it as I can. Increasing them - from 15nF
to 33nF makes the distortion worse. Splitting the resistors into three
rather than two and adding two more capacitors might help, but what this
circuit needs is more insight, rather than more components. >>>>>>>>>>>>
minimal current deviation will have distortion levels orders of >>>>>>>>>>>> magnitude less than the circuit you propose.
Is there any specific reason for the npn Q5?
Replacing it and R25 with a single 100k resistor from U2 to Q1 base seems to work just as well.
2kHz is 141dB down measured with cursors on a zoomed in FFT in LTSPice 24.1.2
Complementary pairs often work better than simple emitter followers. >>>>>>>>>
It's still exploiting the same idea.
The Sziklai pair has been used for centuries.
The Wikipedia page lists a 1957 patent. Transistors had been around for perhaps ten years by then. I got into electronics
around
1966 (as a graduate student in chemistry) and knew about complementary Darlington pairs from early on, though nobody called
them
Sziklai pairs back then.
There's one on page 566 (Pdf page 16)
https://www.worldradiohistory.com/UK/Wireless-World/60s/Wireless-World-1961-11.pdf
John May probably has a good reason for the choice. I've used them from time to time.
https://en.wikipedia.org/wiki/Sziklai_pair
John May's post makes it clear that he didn't have a good reason to go for that arrangement - it was cut and pasted from
from
a
earlier circuit where it did make more sense. He also make it clear that your modification wasn't well thought out - the
100k
resistor isn't required at all, and would degrade the performance of the circuit (though not enough for anybody to notice).
Bill. The current in the resistor is about 500 nA.
Why would the resistor degrade the performance?
The 2N38906 has 10pF of input capacitance and 4.5pF of output capacitance. The resistor introduces about 1usec of lag, which
degrades the high frequency performance.
Which is irrelevant for this circuit.
In a 1kHz oscillator this isn't going to worry anybody,
So why bother pointing it out?
and the LT1013 is slow enough that it won't matter - C9 kills any risk there - but the resistor clearly isn't doing anything
useful, so one has to wonder why you bothered to add it.
That is the question that matters.
But it doesn't matter to anyone else Bill.
What makes you think that? You may find it a comforting thought, but it strikes me a self-serving delusion.
It strikes me as an obvious fact.
I'm not expecting anyone else to offer any comment but it's interesting that they haven't.
And it's not like this group is only for the discussion of electronic matters, as the "Cracking Speech by JDV" thread shows.
You seem to be enjoying yourself there.
In any real circuit I would generally not connect a low impedance output from an op amp directly to the base of a transistor,
but
this doesn't mean that there aren't cases where it's perfectly fine or desirable to do so.
In this case it doesn't matter, so why bother pointing out that it doesn't matter?
You've been complaining that my circuits include too many components, even though each one of the serves a purpose.
So add another hundred ferrites and claim that each one serves a purpose if you want.
I don't mind.
But you still complain about it.
I wouldn't call it complaining. Just pointing out the obvious.
The ferrites do serve a purpose, even if you can't see the point.
Ok let me simulate your mode of response. This is just a simulation, it doesn't mean you actually said this. Here goes.
<Bill>
Why have you included useless ferrites in your circuit?
Even a five year old should be able to see that a simulation with and without all nine ferrites produces exactly the same harmonic
distortion result.
(-57.5dB at 2kHz in LTSPice 24.1.2)
You obviously don't know what those ferrites are doing, and didn't realise that you didn't need them.
</Bill>
You're still only going to get 60dB down in LTSpice 24.1.2
So LTSpice 17 and LTSpice 24 give different results - not a good reason fro trusting either of them. If you want to make a fuss
about harmonic levels you have to measure them in a real circuit, which is expensive and time-consuming. John May has done it -
neither of us have.
You should expect me to complain when one of your circuits includes a useless component which degrades it's performance even itI do too. Then I can put any value resistor in place from 0 ohm to infinity ohm.
it
is only a very minor degradation.
You can also argue that R7 isn't needed, but in any real circuit I would include both resistors.
I can always put 0 ohm in.
I automatically put a resistor in series with the gate of a power MOSFET. >>>
But the circuit won't work if the resistance is too high.
Who cares Bill?
I just put 1 Meg in there and ran a simulation. The result it exactly the same.
I'm not suggesting I'd actually use 1 Meg in practice.
And production want to buying and fit a single resistor value.
This circuit has nothing to do with production.
It exists only in the mind of a few people and the memory of a few computers.
Select on test resistors aren't popular - Cambridge Instruments used them from time to time, and production kept on proposing to
use a fixed resistor.
"From 1960 the company started to decline and struggled to turn a profit." Hmm
We were buying parts in six month chunks, and for that six months production always fitted the same resistor (and got bored). A
new batch of parts would need a different resistor.
Just like the resistor I put between U6 and Q1.
Far from it. You didn't know what it was doing, and didn't realise that you didn't need it.
Now you're starting to border on telling blatant lies Bill.
For example, in the circuit here (which turned up in a search engine search). https://www.eeeguide.com/op-amp-regulators/
The base is connected directly to the transistor.
Yes I know that's not the same circuit as the one in the current mirror but here it's just an example of direct connection to the
base.
My instinct would be to include a base resistor to protect the op amp against failure of the pass transistor.
In the current mirror circuit it doesn't matter whether such a resistor is doing anything or not.
You can easily demonstrate that with a simulation or two.
Why do you enjoy telling other people that they don't know what they're doing Bill?
In any case this resistor doesn't actually exist. As resistors go it's about as real as Ceci n'est pas une pipe.
It only exists in the limited mathematical imagination of the computer in front of
And it's cheaper and quicker to model a circuit that it is to build and test it. Within the limits of the model it's quite useful,
but the game to get to circuit that you can build, which is likely to work. No real circuit? No game.
I think the circuit JM posted is likely to work.
Two BCM61B devices would probably be fine for the current mirror.
A single LT1679 can be used for U1,5,6,8 with a cheaper device for the rest.
And C6 can be made from two polarized capacitors.
Q5, R25, R7 and C9 can be removed but keeping R7, C9 and a base series resistor for Q1 does no harm.
The simulation result in LTSpice 24.1.2 is the same, about -142dB at 2kHz.
Do you have any productive comments yourself?
So getting worked up over its exact value isn't very productive, don't you agree?
If you are silly enough to think like that this isn't going to be a productive discussion, and your part of it hasn't been for
quite a while.
Are you done coming across as a grumpy old headmaster talking to a student who didn't do their homework?
My approach to such a situation would be to offer the student help and encouragement.
But it appears that yours would be along the lines of "You obviously don't know what you're doing you stupid kid" and "What you
should have done is..."
"Bill Sloman" <bill.sloman@ieee.org> wrote in message news:vp4ibd$28rod$1@dont-email.me...
On 19/02/2025 5:40 am, Edward Rawde wrote:
"Bill Sloman" <bill.sloman@ieee.org> wrote in message news:vp1acj$1j5t7$1@dont-email.me...
On 18/02/2025 2:50 pm, Edward Rawde wrote:
"Bill Sloman" <bill.sloman@ieee.org> wrote in message news:vp0svp$1d8re$6@dont-email.me...
On 18/02/2025 3:54 am, Edward Rawde wrote:
"Bill Sloman" <bill.sloman@ieee.org> wrote in message news:voujeq$11678$2@dont-email.me...
On 17/02/2025 3:53 pm, Edward Rawde wrote:
"Bill Sloman" <bill.sloman@ieee.org> wrote in message news:voualf$rm6g$8@dont-email.me...
On 17/02/2025 2:14 am, Edward Rawde wrote:
"Bill Sloman" <bill.sloman@ieee.org> wrote in message news:vorsg8$emeo$7@dont-email.me...
On 16/02/2025 2:18 pm, Edward Rawde wrote:
"JM" <sunaecoNoChoppedPork@gmail.com> wrote in message news:gp6vqjl5oma32tga136kspreh7a8182ofg@4ax.com...
On Mon, 10 Feb 2025 17:18:01 +1100, Bill Sloman <bill.sloman@ieee.org>
wrote:
But it doesn't matter to anyone else Bill.
What makes you think that? You may find it a comforting thought, but it strikes me a self-serving delusion.
It strikes me as an obvious fact.
I'm not expecting anyone else to offer any comment but it's interesting that they haven't.
And it's not like this group is only for the discussion of electronic matters, as the "Cracking Speech by JDV" thread shows.
You seem to be enjoying yourself there.
...
I think the circuit JM posted is likely to work.
Congratulations. You've said something sensible for once.
Why do you like to talk down to other people Bill?
It doesn't make you look superior, far from it.
Two BCM61B devices would probably be fine for the current mirror.
A single LT1679 can be used for U1,5,6,8 with a cheaper device for the rest.
This is a less defensible observation.
After more simulation I agree that all devices may as well be LT1679.
Two quad op amp packages.
This produces the lowest possible distortion in simulation.
U5,U6 and U8 are the phase shift oscillator. U1 should a cheap device that is part of the network that generates the amplitude
feedback signal fed into the integrator wrapped around U7 to generate the gain control signal that modulate the level of the
feedback sine wave that adjusts the output amplitude.
And C6 can be made from two polarized capacitors.
Sadly, you can't buy a pair of 940uF polarised capacitors. Two 1000uf polarised capacitors would be quite close enough
There have been two polarised 1000uf capacitors on my schematic for the last few days.
https://4donline.ihs.com/images/VipMasterIC/IC/VISH/VISH-S-A0010924709
/VISH-S-A0010924709-1.pdf?hkey=6D3A4C79FDBF58556ACFDE234799DDF0
are offered at +/-10% and +/-20% tolerance and 940uF is within 10% of 1000uF.
I(R17) runs at about 100uA and I(R21) runs at about 145uA -that is about 25mV across R17 and 36mV across R21. A single polarised
capacitor isn't going to get depolarised by 11mV of bias.
Putting 100uF polarised caps in parallel to R17 and R19 delivers harmonics about -135dB below the fundamental rather more cheaply,
and won't upset people who get nervous about polarised caps.
As we know, LTSpice isn't all that credible when it predicts very low harmonic content, so 470uF is perhaps a a bit much.
I've have spelled this out quite explicitly from time to time over the twenty years I've been posting here.
I've been reading and posting in this and other groups for way more than 20 years.
On 19/02/2025 11:43 pm, Edward Rawde wrote:
"Bill Sloman" <bill.sloman@ieee.org> wrote in message news:vp4ibd$28rod$1@dont-email.me...
On 19/02/2025 5:40 am, Edward Rawde wrote:
"Bill Sloman" <bill.sloman@ieee.org> wrote in message news:vp1acj$1j5t7$1@dont-email.me...
On 18/02/2025 2:50 pm, Edward Rawde wrote:
"Bill Sloman" <bill.sloman@ieee.org> wrote in message news:vp0svp$1d8re$6@dont-email.me...
On 18/02/2025 3:54 am, Edward Rawde wrote:
"Bill Sloman" <bill.sloman@ieee.org> wrote in message news:voujeq$11678$2@dont-email.me...
On 17/02/2025 3:53 pm, Edward Rawde wrote:
"Bill Sloman" <bill.sloman@ieee.org> wrote in message news:voualf$rm6g$8@dont-email.me...
On 17/02/2025 2:14 am, Edward Rawde wrote:
"Bill Sloman" <bill.sloman@ieee.org> wrote in message news:vorsg8$emeo$7@dont-email.me...
On 16/02/2025 2:18 pm, Edward Rawde wrote:
"JM" <sunaecoNoChoppedPork@gmail.com> wrote in message news:gp6vqjl5oma32tga136kspreh7a8182ofg@4ax.com...
On Mon, 10 Feb 2025 17:18:01 +1100, Bill Sloman <bill.sloman@ieee.org>
wrote:
But it doesn't matter to anyone else Bill.
What makes you think that? You may find it a comforting thought, but it strikes me a self-serving delusion.
It strikes me as an obvious fact.
We can see that, and work out why.
I'm not expecting anyone else to offer any comment but it's interesting that they haven't.
Low distortion 1kHz oscillators are a pretty niche subject. It's pretty much audiophile-specific. I'm not actually an audiophile,
though I got a couple of letter into the UK HiFi News and Record Reviews back in the 1980's, but I got interested by some of the
weirder electronics they touted.
And it's not like this group is only for the discussion of electronic matters, as the "Cracking Speech by JDV" thread shows.
You seem to be enjoying yourself there.
Sending up Cursitor Doom can be fun.
...
I think the circuit JM posted is likely to work.
Congratulations. You've said something sensible for once.
Why do you like to talk down to other people Bill?
I don't especially like doing it but some comments make it unavoidable.
It doesn't make you look superior, far from it.
I don't feel any need to look superior, and scholar google demonstrates that I'm not. My wife has racked up many more citations -
psycholinguistics papers do get cited in larger numbers than my kind of stuff, but that isn't the crucial difference.
https://scholar.google.com.au/scholar?hl=en&as_sdt=0%2C5&q=%22A+W+Sloman%22&btnG=
Two BCM61B devices would probably be fine for the current mirror.
A single LT1679 can be used for U1,5,6,8 with a cheaper device for the rest.
This is a less defensible observation.
After more simulation I agree that all devices may as well be LT1679.
That wasn't what I said, so "agree" isn't the right word. John May uses the cheaper LT1013 outside the oscillator signal path, as
anybody with an sense would.
Two quad op amp packages.
This produces the lowest possible distortion in simulation.
Compared with what?
U5,U6 and U8 are the phase shift oscillator. U1 should a cheap device that is part of the network that generates the amplitude
feedback signal fed into the integrator wrapped around U7 to generate the gain control signal that modulate the level of the
feedback sine wave that adjusts the output amplitude.
And C6 can be made from two polarized capacitors.
Sadly, you can't buy a pair of 940uF polarised capacitors. Two 1000uf polarised capacitors would be quite close enough
There have been two polarised 1000uf capacitors on my schematic for the last few days.
Something of an over-kill.
https://4donline.ihs.com/images/VipMasterIC/IC/VISH/VISH-S-A0010924709
/VISH-S-A0010924709-1.pdf?hkey=6D3A4C79FDBF58556ACFDE234799DDF0
are offered at +/-10% and +/-20% tolerance and 940uF is within 10% of 1000uF.
I(R17) runs at about 100uA and I(R21) runs at about 145uA -that is about 25mV across R17 and 36mV across R21. A single polarised
capacitor isn't going to get depolarised by 11mV of bias.
Putting 100uF polarised caps in parallel to R17 and R19 delivers harmonics about -135dB below the fundamental rather more
cheaply,
and won't upset people who get nervous about polarised caps.
As we know, LTSpice isn't all that credible when it predicts very low harmonic content, so 470uF is perhaps a a bit much.
<snip>
I've have spelled this out quite explicitly from time to time over the twenty years I've been posting here.
I've been reading and posting in this and other groups for way more than 20 years.
These kind of groups haven't been around for "way more than twenty years". I dug my first post here out of google groups some time
ago, and it was in 1996 (some 28 years ago). User groups predate the world wide web, but not by much. I was e-mailing my wife
across Cambridge via Abingdon in the late 1980's but only by virtue of the Alvey project I was tied up with at the time.
--
Bill Sloman, Sydney
"Bill Sloman" <bill.sloman@ieee.org> wrote in message news:vp4ou6$29vt1$1@dont-email.me...
On 19/02/2025 11:43 pm, Edward Rawde wrote:
"Bill Sloman" <bill.sloman@ieee.org> wrote in message news:vp4ibd$28rod$1@dont-email.me...
On 19/02/2025 5:40 am, Edward Rawde wrote:
"Bill Sloman" <bill.sloman@ieee.org> wrote in message news:vp1acj$1j5t7$1@dont-email.me...
On 18/02/2025 2:50 pm, Edward Rawde wrote:
"Bill Sloman" <bill.sloman@ieee.org> wrote in message news:vp0svp$1d8re$6@dont-email.me...
On 18/02/2025 3:54 am, Edward Rawde wrote:
"Bill Sloman" <bill.sloman@ieee.org> wrote in message news:voujeq$11678$2@dont-email.me...
On 17/02/2025 3:53 pm, Edward Rawde wrote:
"Bill Sloman" <bill.sloman@ieee.org> wrote in message news:voualf$rm6g$8@dont-email.me...
On 17/02/2025 2:14 am, Edward Rawde wrote:
"Bill Sloman" <bill.sloman@ieee.org> wrote in message news:vorsg8$emeo$7@dont-email.me...
On 16/02/2025 2:18 pm, Edward Rawde wrote:
"JM" <sunaecoNoChoppedPork@gmail.com> wrote in message news:gp6vqjl5oma32tga136kspreh7a8182ofg@4ax.com...
On Mon, 10 Feb 2025 17:18:01 +1100, Bill Sloman <bill.sloman@ieee.org>
wrote:
But it doesn't matter to anyone else Bill.
What makes you think that? You may find it a comforting thought, but it strikes me a self-serving delusion.
It strikes me as an obvious fact.
We can see that, and work out why.
I'm not expecting anyone else to offer any comment but it's interesting that they haven't.
Low distortion 1kHz oscillators are a pretty niche subject. It's pretty much audiophile-specific. I'm not actually an audiophile,
though I got a couple of letter into the UK HiFi News and Record Reviews back in the 1980's, but I got interested by some of the
weirder electronics they touted.
And it's not like this group is only for the discussion of electronic matters, as the "Cracking Speech by JDV" thread shows.
You seem to be enjoying yourself there.
Sending up Cursitor Doom can be fun.
Which suggests that you enjoy being unpleasant.
...
I think the circuit JM posted is likely to work.
Congratulations. You've said something sensible for once.
Why do you like to talk down to other people Bill?
I don't especially like doing it but some comments make it unavoidable.
Which suggests that unpleasantness is just part of your personality.
It doesn't make you look superior, far from it.
I don't feel any need to look superior, and scholar google demonstrates that I'm not. My wife has racked up many more citations -
psycholinguistics papers do get cited in larger numbers than my kind of stuff, but that isn't the crucial difference.
https://scholar.google.com.au/scholar?hl=en&as_sdt=0%2C5&q=%22A+W+Sloman%22&btnG=
Two BCM61B devices would probably be fine for the current mirror.
A single LT1679 can be used for U1,5,6,8 with a cheaper device for the rest.
This is a less defensible observation.
After more simulation I agree that all devices may as well be LT1679.
That wasn't what I said, so "agree" isn't the right word. John May uses the cheaper LT1013 outside the oscillator signal path, as
anybody with an sense would.
Anybody with any sense would look at the economics and go for the lowest possible cost when choosing between LT1678, LT1679, LT1013,
LT1014
It's nice to have a circuit ready for a practical build but I won't be building it myself.
Two quad op amp packages.
This produces the lowest possible distortion in simulation.
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