Hi, All,
Late last year we did a fast sampler/TDR with nice clean 60 ps edges.
We're gearing up to actually sell them, so I did a short technical
writeup on the design, which may be of interest.
<https://electrooptical.net/News/a-high-performance-time-domain-reflectometer>
Cheers
Phil Hobbs
Hi, All,
Late last year we did a fast sampler/TDR with nice clean 60 ps edges.
We're gearing up to actually sell them, so I did a short technical
writeup on the design, which may be of interest.
<https://electrooptical.net/News/a-high-performance-time-domain-reflectometer>
On Wed, 5 Mar 2025 18:20:47 -0500, Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:
Hi, All,
Late last year we did a fast sampler/TDR with nice clean 60 ps edges.
We're gearing up to actually sell them, so I did a short technical
writeup on the design, which may be of interest.
<https://electrooptical.net/News/a-high-performance-time-domain-reflectometer>
Neat. No step-recovery diodes.
The LVDS line receivers are radical parts, for 30 cents.
We also used ATLC2 to get a good match of a cheap fat-pin edge-launch
SMA connector to a multilayer PCB. That was fun.
On 2025-03-05 19:15, john larkin wrote:
On Wed, 5 Mar 2025 18:20:47 -0500, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:
Hi, All,
Late last year we did a fast sampler/TDR with nice clean 60 ps edges.
We're gearing up to actually sell them, so I did a short technical
writeup on the design, which may be of interest.
<https://electrooptical.net/News/a-high-performance-time-domain-reflectometer>
Neat. No step-recovery diodes.
Well, 40 years does get you something sometimes. ;)
On 3/5/25 5:00 PM, Phil Hobbs wrote:
On 2025-03-05 19:15, john larkin wrote:
On Wed, 5 Mar 2025 18:20:47 -0500, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:
Hi, All,
Late last year we did a fast sampler/TDR with nice clean 60 ps edges.
We're gearing up to actually sell them, so I did a short technical
writeup on the design, which may be of interest.
<https://electrooptical.net/News/a-high-performance-time-domain-reflectometer>
Neat. No step-recovery diodes.
Well, 40 years does get you something sometimes. ;)
And those cheap yet blazingly fast RF transistors, thanks to cell phones
and all. They make nice pulsers. But they are like the princess on the
pea, very low Vce and if you go a smidgen above ... poof.
[...]
Hi, All,
Late last year we did a fast sampler/TDR with nice clean 60 ps edges.
We're gearing up to actually sell them, so I did a short technical
writeup on the design, which may be of interest.
<https://electrooptical.net/News/a-high-performance-time-domain-reflectometer>
On 2025-03-05 20:07, Joerg wrote:
On 3/5/25 5:00 PM, Phil Hobbs wrote:
On 2025-03-05 19:15, john larkin wrote:
On Wed, 5 Mar 2025 18:20:47 -0500, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:
Hi, All,
Late last year we did a fast sampler/TDR with nice clean 60 ps edges. >>>>>
We're gearing up to actually sell them, so I did a short technical
writeup on the design, which may be of interest.
<https://electrooptical.net/News/a-high-performance-time-domain-reflectometer>
Neat. No step-recovery diodes.
Well, 40 years does get you something sometimes. ;)
And those cheap yet blazingly fast RF transistors, thanks to cell phones
and all. They make nice pulsers. But they are like the princess on the
pea, very low Vce and if you go a smidgen above ... poof.
[...]
They're not that bad, really--their betas are so high that BV_CEO is
lowish, but BV_CBO is 12 volts or more. Their saturation behavior is
still pretty BJTish, though. ;)
Cheers
Phil Hobbs
On Wed, 5 Mar 2025 20:10:08 -0500, Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:
On 2025-03-05 20:07, Joerg wrote:
On 3/5/25 5:00 PM, Phil Hobbs wrote:
On 2025-03-05 19:15, john larkin wrote:
On Wed, 5 Mar 2025 18:20:47 -0500, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:
Hi, All,
Late last year we did a fast sampler/TDR with nice clean 60 ps edges. >>>>>>
We're gearing up to actually sell them, so I did a short technical >>>>>> writeup on the design, which may be of interest.
<https://electrooptical.net/News/a-high-performance-time-domain-reflectometer>
Neat. No step-recovery diodes.
Well, 40 years does get you something sometimes. ;)
And those cheap yet blazingly fast RF transistors, thanks to cell phones >>> and all. They make nice pulsers. But they are like the princess on the
pea, very low Vce and if you go a smidgen above ... poof.
[...]
They're not that bad, really--their betas are so high that BV_CEO is
lowish, but BV_CBO is 12 volts or more. Their saturation behavior is
still pretty BJTish, though. ;)
Cheers
Phil Hobbs
I toyed with the idea of using a PHEMT as a series-switch fast sample-and-hold.
Hey, here's another goofy idea:
We used to make fast linear ramps, driving a comparator against a DAC,
as a programmable delay. But we got smarter and just used an RC
charging thing, and mucked the DAC codes with a polynomial to get our
delay.
But what if the comparator sees a fast RC on one input and a slow RC
on the other? The exponential curves cancel, and you get a nice slow
linear sampling timebase. If you don't quibble too much.
john larkin <jl@650pot.com> wrote:
On Wed, 5 Mar 2025 20:10:08 -0500, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:
On 2025-03-05 20:07, Joerg wrote:
On 3/5/25 5:00 PM, Phil Hobbs wrote:
On 2025-03-05 19:15, john larkin wrote:
On Wed, 5 Mar 2025 18:20:47 -0500, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:
Hi, All,
Late last year we did a fast sampler/TDR with nice clean 60 ps edges. >>>>>>>
We're gearing up to actually sell them, so I did a short technical >>>>>>> writeup on the design, which may be of interest.
<https://electrooptical.net/News/a-high-performance-time-domain-reflectometer>
Neat. No step-recovery diodes.
Well, 40 years does get you something sometimes. ;)
And those cheap yet blazingly fast RF transistors, thanks to cell phones >>>> and all. They make nice pulsers. But they are like the princess on the >>>> pea, very low Vce and if you go a smidgen above ... poof.
[...]
They're not that bad, really--their betas are so high that BV_CEO is
lowish, but BV_CBO is 12 volts or more. Their saturation behavior is
still pretty BJTish, though. ;)
Cheers
Phil Hobbs
I toyed with the idea of using a PHEMT as a series-switch fast
sample-and-hold.
They work well for that. A couple of years back, we did a POC for the Navy that used several SAV551pluses—100 ps is doable. The main problem is that their voltage gain is lowish, so you don’t get as much speedup as with a BJT.
And of course they’re 10x the price.
Hey, here's another goofy idea:
We used to make fast linear ramps, driving a comparator against a DAC,
as a programmable delay. But we got smarter and just used an RC
charging thing, and mucked the DAC codes with a polynomial to get our
delay.
But what if the comparator sees a fast RC on one input and a slow RC
on the other? The exponential curves cancel, and you get a nice slow
linear sampling timebase. If you don't quibble too much.
Not sure about that. For the proto, I used a ramp from an arb to make the threshold—the sampling loop converged at each point, so I wound up with a 10**7:1 zoom—10 us per picosecond.
The fast bit was all over before the slow bit moved perceptibly.
Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:
john larkin <jl@650pot.com> wrote:
On Wed, 5 Mar 2025 20:10:08 -0500, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:
On 2025-03-05 20:07, Joerg wrote:
On 3/5/25 5:00 PM, Phil Hobbs wrote:
On 2025-03-05 19:15, john larkin wrote:
On Wed, 5 Mar 2025 18:20:47 -0500, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:
Hi, All,
Late last year we did a fast sampler/TDR with nice clean 60 ps edges. >>>>>>>>
We're gearing up to actually sell them, so I did a short technical >>>>>>>> writeup on the design, which may be of interest.
<https://electrooptical.net/News/a-high-performance-time-domain-reflectometer>
Neat. No step-recovery diodes.
Well, 40 years does get you something sometimes. ;)
And those cheap yet blazingly fast RF transistors, thanks to cell phones >>>>> and all. They make nice pulsers. But they are like the princess on the >>>>> pea, very low Vce and if you go a smidgen above ... poof.
[...]
They're not that bad, really--their betas are so high that BV_CEO is
lowish, but BV_CBO is 12 volts or more. Their saturation behavior is
still pretty BJTish, though. ;)
Cheers
Phil Hobbs
I toyed with the idea of using a PHEMT as a series-switch fast
sample-and-hold.
They work well for that. A couple of years back, we did a POC for the Navy >> that used several SAV551pluses—100 ps is doable. The main problem is that
their voltage gain is lowish, so you don’t get as much speedup as with a
BJT.
And of course they’re 10x the price.
Hey, here's another goofy idea:
We used to make fast linear ramps, driving a comparator against a DAC,
as a programmable delay. But we got smarter and just used an RC
charging thing, and mucked the DAC codes with a polynomial to get our
delay.
But what if the comparator sees a fast RC on one input and a slow RC
on the other? The exponential curves cancel, and you get a nice slow
linear sampling timebase. If you don't quibble too much.
Not sure about that. For the proto, I used a ramp from an arb to make the >> threshold—the sampling loop converged at each point, so I wound up with a
10**7:1 zoom—10 us per picosecond.
The fast bit was all over before the slow bit moved perceptibly.
The other issue is that the prop delay depends on the overdrive. Since
we’re comparing a ramp to a fixed threshold, which that basically means how >far the ramp rises during the time required for the positive feedback to
get going.
So we still need an online calibration. Fortunately that isn’t hard—an >open-circuited bit of coax is enough. It doesn’t have to be done often.
Cheers
Phil Hobbs
On Thu, 6 Mar 2025 14:53:43 -0000 (UTC), Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:
Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:
john larkin <jl@650pot.com> wrote:
On Wed, 5 Mar 2025 20:10:08 -0500, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:
On 2025-03-05 20:07, Joerg wrote:
On 3/5/25 5:00 PM, Phil Hobbs wrote:
On 2025-03-05 19:15, john larkin wrote:
On Wed, 5 Mar 2025 18:20:47 -0500, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:
Hi, All,
Late last year we did a fast sampler/TDR with nice clean 60 ps edges. >>>>>>>>>
We're gearing up to actually sell them, so I did a short technical >>>>>>>>> writeup on the design, which may be of interest.
<https://electrooptical.net/News/a-high-performance-time-domain-reflectometer>
Neat. No step-recovery diodes.
Well, 40 years does get you something sometimes. ;)
And those cheap yet blazingly fast RF transistors, thanks to cell phones >>>>>> and all. They make nice pulsers. But they are like the princess on the >>>>>> pea, very low Vce and if you go a smidgen above ... poof.
[...]
They're not that bad, really--their betas are so high that BV_CEO is >>>>> lowish, but BV_CBO is 12 volts or more. Their saturation behavior is >>>>> still pretty BJTish, though. ;)
Cheers
Phil Hobbs
I toyed with the idea of using a PHEMT as a series-switch fast
sample-and-hold.
They work well for that. A couple of years back, we did a POC for the Navy >>> that used several SAV551pluses—100 ps is doable. The main problem is that >>> their voltage gain is lowish, so you don’t get as much speedup as with a >>> BJT.
And of course they’re 10x the price.
Hey, here's another goofy idea:
We used to make fast linear ramps, driving a comparator against a DAC, >>>> as a programmable delay. But we got smarter and just used an RC
charging thing, and mucked the DAC codes with a polynomial to get our
delay.
But what if the comparator sees a fast RC on one input and a slow RC
on the other? The exponential curves cancel, and you get a nice slow
linear sampling timebase. If you don't quibble too much.
Not sure about that. For the proto, I used a ramp from an arb to make the >>> threshold—the sampling loop converged at each point, so I wound up with a >>> 10**7:1 zoom—10 us per picosecond.
The fast bit was all over before the slow bit moved perceptibly.
The other issue is that the prop delay depends on the overdrive. Since
we’re comparing a ramp to a fixed threshold, which that basically means how
far the ramp rises during the time required for the positive feedback to
get going.
So we still need an online calibration. Fortunately that isn’t hard—an >> open-circuited bit of coax is enough. It doesn’t have to be done often.
Cheers
Phil Hobbs
I did caution about quibbling too much. One issue is that the LVDS
line receivers have a bunch of offset as the common-mode voltage
approaches the positive supply rail. And of course the esd diodes are nonlinear capacitors. And things always ring a little. Geez, nobody's perfect.
One of my guys did a bunch experiments using an LVDS receiver as the comparator in a picosecond-resolution delay circuit. We use a 16-bit
DAC and a 4th order polynomial and calibrate the polynomial for every channel. Our P500 has, I recall, nine of those.
https://highlandtechnology.com/Product/P500
When I was young and foolish, I used to do time delays with linear
ramps and ECL comparators.
On 2025-03-06 10:24, john larkin wrote:
On Thu, 6 Mar 2025 14:53:43 -0000 (UTC), Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:
Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:
john larkin <jl@650pot.com> wrote:
On Wed, 5 Mar 2025 20:10:08 -0500, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:
On 2025-03-05 20:07, Joerg wrote:
On 3/5/25 5:00 PM, Phil Hobbs wrote:
On 2025-03-05 19:15, john larkin wrote:
On Wed, 5 Mar 2025 18:20:47 -0500, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:
Hi, All,
Late last year we did a fast sampler/TDR with nice clean 60 ps edges.
We're gearing up to actually sell them, so I did a short technical >>>>>>>>>> writeup on the design, which may be of interest.
<https://electrooptical.net/News/a-high-performance-time-domain-reflectometer>
Neat. No step-recovery diodes.
Well, 40 years does get you something sometimes. ;)
And those cheap yet blazingly fast RF transistors, thanks to cell phones
and all. They make nice pulsers. But they are like the princess on the >>>>>>> pea, very low Vce and if you go a smidgen above ... poof.
[...]
They're not that bad, really--their betas are so high that BV_CEO is >>>>>> lowish, but BV_CBO is 12 volts or more. Their saturation behavior is >>>>>> still pretty BJTish, though. ;)
Cheers
Phil Hobbs
I toyed with the idea of using a PHEMT as a series-switch fast
sample-and-hold.
They work well for that. A couple of years back, we did a POC for the Navy >>>> that used several SAV551pluses—100 ps is doable. The main problem is that >>>> their voltage gain is lowish, so you don’t get as much speedup as with a >>>> BJT.
And of course they’re 10x the price.
Hey, here's another goofy idea:
We used to make fast linear ramps, driving a comparator against a DAC, >>>>> as a programmable delay. But we got smarter and just used an RC
charging thing, and mucked the DAC codes with a polynomial to get our >>>>> delay.
But what if the comparator sees a fast RC on one input and a slow RC >>>>> on the other? The exponential curves cancel, and you get a nice slow >>>>> linear sampling timebase. If you don't quibble too much.
Not sure about that. For the proto, I used a ramp from an arb to make the >>>> threshold—the sampling loop converged at each point, so I wound up with a >>>> 10**7:1 zoom—10 us per picosecond.
The fast bit was all over before the slow bit moved perceptibly.
The other issue is that the prop delay depends on the overdrive. Since
we’re comparing a ramp to a fixed threshold, which that basically means how >>> far the ramp rises during the time required for the positive feedback to >>> get going.
So we still need an online calibration. Fortunately that isn’t hard—an
open-circuited bit of coax is enough. It doesn’t have to be done often.
Cheers
Phil Hobbs
I did caution about quibbling too much. One issue is that the LVDS
line receivers have a bunch of offset as the common-mode voltage
approaches the positive supply rail. And of course the esd diodes are
nonlinear capacitors. And things always ring a little. Geez, nobody's
perfect.
One of my guys did a bunch experiments using an LVDS receiver as the
comparator in a picosecond-resolution delay circuit. We use a 16-bit
DAC and a 4th order polynomial and calibrate the polynomial for every
channel. Our P500 has, I recall, nine of those.
https://highlandtechnology.com/Product/P500
When I was young and foolish, I used to do time delays with linear
ramps and ECL comparators.
The line receivers don't seem to have any significant amount of kickout, >either--we can sweep the Rx pulse across the Tx pulse with no apparent >funnies due to interaction. Have you folks seen any kickout issues?
Of course the kickout might be delayed, I suppose.
Cheers
Phil Hobbs
On Thu, 6 Mar 2025 10:54:20 -0500, Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:
On 2025-03-06 10:24, john larkin wrote:
On Thu, 6 Mar 2025 14:53:43 -0000 (UTC), Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:
Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:
john larkin <jl@650pot.com> wrote:
On Wed, 5 Mar 2025 20:10:08 -0500, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:
On 2025-03-05 20:07, Joerg wrote:
On 3/5/25 5:00 PM, Phil Hobbs wrote:
On 2025-03-05 19:15, john larkin wrote:
On Wed, 5 Mar 2025 18:20:47 -0500, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:
Hi, All,
Late last year we did a fast sampler/TDR with nice clean 60 ps edges.
We're gearing up to actually sell them, so I did a short technical >>>>>>>>>>> writeup on the design, which may be of interest.
<https://electrooptical.net/News/a-high-performance-time-domain-reflectometer>
Neat. No step-recovery diodes.
Well, 40 years does get you something sometimes. ;)
And those cheap yet blazingly fast RF transistors, thanks to cell phones
and all. They make nice pulsers. But they are like the princess on the >>>>>>>> pea, very low Vce and if you go a smidgen above ... poof.
[...]
They're not that bad, really--their betas are so high that BV_CEO is >>>>>>> lowish, but BV_CBO is 12 volts or more. Their saturation behavior is >>>>>>> still pretty BJTish, though. ;)
Cheers
Phil Hobbs
I toyed with the idea of using a PHEMT as a series-switch fast
sample-and-hold.
They work well for that. A couple of years back, we did a POC for the Navy
that used several SAV551pluses—100 ps is doable. The main problem is that
their voltage gain is lowish, so you don’t get as much speedup as with a
BJT.
And of course they’re 10x the price.
Hey, here's another goofy idea:
We used to make fast linear ramps, driving a comparator against a DAC, >>>>>> as a programmable delay. But we got smarter and just used an RC
charging thing, and mucked the DAC codes with a polynomial to get our >>>>>> delay.
But what if the comparator sees a fast RC on one input and a slow RC >>>>>> on the other? The exponential curves cancel, and you get a nice slow >>>>>> linear sampling timebase. If you don't quibble too much.
Not sure about that. For the proto, I used a ramp from an arb to make the
threshold—the sampling loop converged at each point, so I wound up with a
10**7:1 zoom—10 us per picosecond.
The fast bit was all over before the slow bit moved perceptibly.
The other issue is that the prop delay depends on the overdrive. Since >>>> we’re comparing a ramp to a fixed threshold, which that basically means how
far the ramp rises during the time required for the positive feedback to >>>> get going.
So we still need an online calibration. Fortunately that isn’t hard—an >>>> open-circuited bit of coax is enough. It doesn’t have to be done often. >>>>
Cheers
Phil Hobbs
I did caution about quibbling too much. One issue is that the LVDS
line receivers have a bunch of offset as the common-mode voltage
approaches the positive supply rail. And of course the esd diodes are
nonlinear capacitors. And things always ring a little. Geez, nobody's
perfect.
One of my guys did a bunch experiments using an LVDS receiver as the
comparator in a picosecond-resolution delay circuit. We use a 16-bit
DAC and a 4th order polynomial and calibrate the polynomial for every
channel. Our P500 has, I recall, nine of those.
https://highlandtechnology.com/Product/P500
When I was young and foolish, I used to do time delays with linear
ramps and ECL comparators.
The line receivers don't seem to have any significant amount of kickout,
either--we can sweep the Rx pulse across the Tx pulse with no apparent
funnies due to interaction. Have you folks seen any kickout issues?
Of course the kickout might be delayed, I suppose.
Cheers
Phil Hobbs
We didn't test for that. When a comparator fires, all sorts of stuff
happens downstream, that could jostle adjacent channels.
Our comparators typically drive a 1 ns Tiny Logic flipflop as the next
step in the signal chain.
Standard ECL wasn't as fast as 15 cent Tiny parts are now.
On 3/6/25 8:29 AM, Bill Sloman wrote:
On 7/03/2025 3:06 am, john larkin wrote:
On Thu, 6 Mar 2025 10:54:20 -0500, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:
On 2025-03-06 10:24, john larkin wrote:
[...]
When I was young and foolish, I used to do time delays with linear
ramps and ECL comparators.
The line receivers don't seem to have any significant amount of kickout, >>>> either--we can sweep the Rx pulse across the Tx pulse with no apparent >>>> funnies due to interaction. Have you folks seen any kickout issues?
Of course the kickout might be delayed, I suppose.
Cheers
Phil Hobbs
We didn't test for that. When a comparator fires, all sorts of stuff
happens downstream, that could jostle adjacent channels.
Our comparators typically drive a 1 ns Tiny Logic flipflop as the next
step in the signal chain.
Standard ECL wasn't as fast as 15 cent Tiny parts are now.
But it's current steering logic and the supply rails stay a lot cleaner
than you see with CMOS switches.
Not a big problem, just place pillows around it, RC filters on the
supply. Drive was never an issue in my case but on rare occasions I have
used cheap signal transformers to isolate that.
The larger concern with supply rails is low frequency noise coming in, >causing phase noise. That is where capacitance multipliers can shine.
And what's Standard ECL now? It was Motorola 10k back when I was young,
and Motorola/Philips/Fairchild 100k a few years later. Motorola ECLinPs
took over a about when I stopped using it, about when I started posting
here, some twenty years ago.
AFAIK it's 100E but I have not used any in ages because I always found
them overpriced. I don't like it when two ICs cost more than a crate of
beer :-)
On 7/03/2025 3:06 am, john larkin wrote:
On Thu, 6 Mar 2025 10:54:20 -0500, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:
On 2025-03-06 10:24, john larkin wrote:
When I was young and foolish, I used to do time delays with linear
ramps and ECL comparators.
The line receivers don't seem to have any significant amount of kickout, >>> either--we can sweep the Rx pulse across the Tx pulse with no apparent
funnies due to interaction. Have you folks seen any kickout issues?
Of course the kickout might be delayed, I suppose.
Cheers
Phil Hobbs
We didn't test for that. When a comparator fires, all sorts of stuff
happens downstream, that could jostle adjacent channels.
Our comparators typically drive a 1 ns Tiny Logic flipflop as the next
step in the signal chain.
Standard ECL wasn't as fast as 15 cent Tiny parts are now.
But it's current steering logic and the supply rails stay a lot cleaner
than you see with CMOS switches.
And what's Standard ECL now? It was Motorola 10k back when I was young,
and Motorola/Philips/Fairchild 100k a few years later. Motorola ECLinPs
took over a about when I stopped using it, about when I started posting
here, some twenty years ago.
On Thu, 6 Mar 2025 12:33:35 -0800, Joerg <news@analogconsultants.com>
wrote:
On 3/6/25 8:29 AM, Bill Sloman wrote:
On 7/03/2025 3:06 am, john larkin wrote:
On Thu, 6 Mar 2025 10:54:20 -0500, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:
On 2025-03-06 10:24, john larkin wrote:
[...]
When I was young and foolish, I used to do time delays with linear >>>>>> ramps and ECL comparators.
The line receivers don't seem to have any significant amount of kickout, >>>>> either--we can sweep the Rx pulse across the Tx pulse with no apparent >>>>> funnies due to interaction. Have you folks seen any kickout issues? >>>>>
Of course the kickout might be delayed, I suppose.
Cheers
Phil Hobbs
We didn't test for that. When a comparator fires, all sorts of stuff
happens downstream, that could jostle adjacent channels.
Our comparators typically drive a 1 ns Tiny Logic flipflop as the next >>>> step in the signal chain.
Standard ECL wasn't as fast as 15 cent Tiny parts are now.
But it's current steering logic and the supply rails stay a lot cleaner
than you see with CMOS switches.
Not a big problem, just place pillows around it, RC filters on the
supply. Drive was never an issue in my case but on rare occasions I have
used cheap signal transformers to isolate that.
The larger concern with supply rails is low frequency noise coming in,
causing phase noise. That is where capacitance multipliers can shine.
I measured one FPGA at around 1 mV per picosecond prop delay, on the 1
volt core supply. Prop delay is about inverse on voltage in cmos.
And what's Standard ECL now? It was Motorola 10k back when I was young,
and Motorola/Philips/Fairchild 100k a few years later. Motorola ECLinPs
took over a about when I stopped using it, about when I started posting
here, some twenty years ago.
AFAIK it's 100E but I have not used any in ages because I always found
them overpriced. I don't like it when two ICs cost more than a crate of
beer :-)
MC10EPxx, SiGe Eclips Lite.
Really fast and really expensive is Gigacomm, which is actually CML.
The NB7V52M flop is only about $13 in quantity.
On 3/6/25 12:51 PM, john larkin wrote:
On Thu, 6 Mar 2025 12:33:35 -0800, Joerg <news@analogconsultants.com>
wrote:
On 3/6/25 8:29 AM, Bill Sloman wrote:
On 7/03/2025 3:06 am, john larkin wrote:
On Thu, 6 Mar 2025 10:54:20 -0500, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:
On 2025-03-06 10:24, john larkin wrote:
[...]
When I was young and foolish, I used to do time delays with linear >>>>>>> ramps and ECL comparators.
The line receivers don't seem to have any significant amount of kickout, >>>>>> either--we can sweep the Rx pulse across the Tx pulse with no apparent >>>>>> funnies due to interaction. Have you folks seen any kickout issues? >>>>>>
Of course the kickout might be delayed, I suppose.
Cheers
Phil Hobbs
We didn't test for that. When a comparator fires, all sorts of stuff >>>>> happens downstream, that could jostle adjacent channels.
Our comparators typically drive a 1 ns Tiny Logic flipflop as the next >>>>> step in the signal chain.
Standard ECL wasn't as fast as 15 cent Tiny parts are now.
But it's current steering logic and the supply rails stay a lot cleaner >>>> than you see with CMOS switches.
Not a big problem, just place pillows around it, RC filters on the
supply. Drive was never an issue in my case but on rare occasions I have >>> used cheap signal transformers to isolate that.
The larger concern with supply rails is low frequency noise coming in,
causing phase noise. That is where capacitance multipliers can shine.
I measured one FPGA at around 1 mV per picosecond prop delay, on the 1
volt core supply. Prop delay is about inverse on voltage in cmos.
In my last TDR psec-jitter would have made the client unhappy. The
sampling window was 100psec but it wasn't supposed to move unless told to.
And what's Standard ECL now? It was Motorola 10k back when I was young, >>>> and Motorola/Philips/Fairchild 100k a few years later. Motorola ECLinPs >>>> took over a about when I stopped using it, about when I started posting >>>> here, some twenty years ago.
AFAIK it's 100E but I have not used any in ages because I always found
them overpriced. I don't like it when two ICs cost more than a crate of
beer :-)
MC10EPxx, SiGe Eclips Lite.
Really fast and really expensive is Gigacomm, which is actually CML.
The NB7V52M flop is only about $13 in quantity.
So far I've only needed "semi-analog", meaning just one bit and then I
did it using RF transistors. It is amazing, you can buy >100GHz fT for
less than 20 cents in qties.
When I was a kid I had to shell out around $3 for an AF116 Ge-transistor
that had an fT of 75MHz. In 1970's Dollars, which really hurt. Digital
wasn't any better. I needed a 1kbit RAM for a project and that set me
back about 10 bucks. It still works.
On Thu, 6 Mar 2025 14:12:14 -0800, Joerg <news@analogconsultants.com>
wrote:
On 3/6/25 12:51 PM, john larkin wrote:
On Thu, 6 Mar 2025 12:33:35 -0800, Joerg <news@analogconsultants.com>
wrote:
On 3/6/25 8:29 AM, Bill Sloman wrote:
And what's Standard ECL now? It was Motorola 10k back when I was young, >>>>> and Motorola/Philips/Fairchild 100k a few years later. Motorola ECLinPs >>>>> took over a about when I stopped using it, about when I started posting >>>>> here, some twenty years ago.
AFAIK it's 100E but I have not used any in ages because I always found >>>> them overpriced. I don't like it when two ICs cost more than a crate of >>>> beer :-)
MC10EPxx, SiGe Eclips Lite.
Really fast and really expensive is Gigacomm, which is actually CML.
The NB7V52M flop is only about $13 in quantity.
So far I've only needed "semi-analog", meaning just one bit and then I
did it using RF transistors. It is amazing, you can buy >100GHz fT for
less than 20 cents in qties.
When I was a kid I had to shell out around $3 for an AF116 Ge-transistor
that had an fT of 75MHz. In 1970's Dollars, which really hurt. Digital
wasn't any better. I needed a 1kbit RAM for a project and that set me
back about 10 bucks. It still works.
My first transistor was a Raytheon CK722 germanium. I think Ft was
measured in KHz. It cost $7, about a month's allowance, or dinner for
two at a decent restaurant.
I got tubes for free.
Hi, All,
Late last year we did a fast sampler/TDR with nice clean 60 ps edges.
We're gearing up to actually sell them, so I did a short technical
writeup on the design, which may be of interest.
<https://electrooptical.net/News/a-high-performance-time-domain-reflectometer>
Cheers
Phil Hobbs
Phil Hobbs wrote:
Hi, All,
Late last year we did a fast sampler/TDR with nice clean 60 ps edges.
We're gearing up to actually sell them, so I did a short technical
writeup on the design, which may be of interest.
<https://electrooptical.net/News/a-high-performance-time-domain-reflectometer>
Cheers
Phil Hobbs
Why is a LASER ruler that can measure distances in air with 2mm accuracy
$16,
and an OTDR for measuring fiber $600?
Phil Hobbs wrote:
Hi, All,
Late last year we did a fast sampler/TDR with nice clean 60 ps edges.
We're gearing up to actually sell them, so I did a short technical
writeup on the design, which may be of interest.
<https://electrooptical.net/News/a-high-performance-time-domain-reflectometer>
Cheers
Phil Hobbs
Why is a LASER ruler that can measure distances in air with 2mm accuracy
$16,
and an OTDR for measuring fiber $600?
Phil Hobbs wrote:
Hi, All,
Late last year we did a fast sampler/TDR with nice clean 60 ps edges.
We're gearing up to actually sell them, so I did a short technical
writeup on the design, which may be of interest.
<https://electrooptical.net/News/a-high-performance-time-domain-reflectometer>
Cheers
Phil Hobbs
Why is a LASER ruler that can measure distances in air with 2mm accuracy
$16,
and an OTDR for measuring fiber $600?
On Sun, 9 Mar 2025 19:22:19 -0400, "Tom Del Rosso" <fizzbintuesday@that-google-mail-domain.com> wrote:
Phil Hobbs wrote:
Hi, All,
Late last year we did a fast sampler/TDR with nice clean 60 ps edges.
We're gearing up to actually sell them, so I did a short technical
writeup on the design, which may be of interest.
<https://electrooptical.net/News/a-high-performance-time-domain-reflectometer>
Cheers
Phil Hobbs
Why is a LASER ruler that can measure distances in air with 2mm accuracy
$16,
and an OTDR for measuring fiber $600?
Most rangefinders use sine modulation and measure phase shift, which
doesn't involve picosecond timing or expensive wideband signal
processing. And they report one number, not a graph. OTDRs are much
more complex than rangefinders.
And the markets are different too.
On 2025-03-09 19:22, Tom Del Rosso wrote:
Phil Hobbs wrote:
Hi, All,
Late last year we did a fast sampler/TDR with nice clean 60 ps edges.
We're gearing up to actually sell them, so I did a short technical
writeup on the design, which may be of interest.
<https://electrooptical.net/News/a-high-performance-time-domain-reflectometer>
Cheers
Phil Hobbs
Why is a LASER ruler that can measure distances in air with 2mm accuracy
$16,
and an OTDR for measuring fiber $600?
Well, the OTDR needs a fiber-coupled laser, for one thing, and a decent
TIA. Also as John says, it's a time-domain instrument. A laser ruler
can just be a diode laser with a monitor photodiode, a collimating lens,
a simple TIA and a micro with built-in ADC.
You put a small (1-3 mA) current ramp on the laser, and look at the beat >signal coming out of the monitor photodiode. The frequency gives you
the round-trip delay. This sort of laser feedback measurement can be
pretty good if the diode stays reasonably single-mode.
I have no idea how the $16 ones do it, but if I were building one,
that's the first thing I'd try.
Cheers
Phil Hobbs
On Tue, 11 Mar 2025 14:12:51 -0400, Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:
On 2025-03-09 19:22, Tom Del Rosso wrote:
Phil Hobbs wrote:
Hi, All,
Late last year we did a fast sampler/TDR with nice clean 60 ps edges.
We're gearing up to actually sell them, so I did a short technical
writeup on the design, which may be of interest.
<https://electrooptical.net/News/a-high-performance-time-domain-reflectometer>
Cheers
Phil Hobbs
Why is a LASER ruler that can measure distances in air with 2mm accuracy >>> $16,
and an OTDR for measuring fiber $600?
Well, the OTDR needs a fiber-coupled laser, for one thing, and a decent
TIA. Also as John says, it's a time-domain instrument. A laser ruler
can just be a diode laser with a monitor photodiode, a collimating lens,
a simple TIA and a micro with built-in ADC.
You put a small (1-3 mA) current ramp on the laser, and look at the beat
signal coming out of the monitor photodiode. The frequency gives you
the round-trip delay. This sort of laser feedback measurement can be
pretty good if the diode stays reasonably single-mode.
I have no idea how the $16 ones do it, but if I were building one,
that's the first thing I'd try.
Cheers
Phil Hobbs
I wonder if you even need a photodiode.
Reminds me of the 3-tube proximity fuse, where the plate current of an
RF oscillator was modlated by doppler from a target airplane. Or the
ground.
On 2025-03-09 19:22, Tom Del Rosso wrote:
Phil Hobbs wrote:
Hi, All,
Late last year we did a fast sampler/TDR with nice clean 60 ps edges.
We're gearing up to actually sell them, so I did a short technical
writeup on the design, which may be of interest.
<https://electrooptical.net/News/a-high-performance-time-domain-
reflectometer>
Cheers
Phil Hobbs
Why is a LASER ruler that can measure distances in air with 2mm accuracy
$16,
and an OTDR for measuring fiber $600?
Well, the OTDR needs a fiber-coupled laser, for one thing, and a decent TIA. Also as John says, it's a time-domain instrument. A laser ruler
can just be a diode laser with a monitor photodiode, a collimating lens,
a simple TIA and a micro with built-in ADC.
You put a small (1-3 mA) current ramp on the laser, and look at the beat signal coming out of the monitor photodiode. The frequency gives you
the round-trip delay. This sort of laser feedback measurement can be
pretty good if the diode stays reasonably single-mode.
I have no idea how the $16 ones do it, but if I were building one,
that's the first thing I'd try.
Cheers
Phil Hobbs
On 2025-03-09 19:22, Tom Del Rosso wrote:
Phil Hobbs wrote:
Hi, All,
Late last year we did a fast sampler/TDR with nice clean 60 ps edges.
We're gearing up to actually sell them, so I did a short technical
writeup on the design, which may be of interest.
<https://electrooptical.net/News/a-high-performance-time-domain-reflectometer>
Cheers
Phil Hobbs
Why is a LASER ruler that can measure distances in air with 2mm accuracy
$16,
and an OTDR for measuring fiber $600?
Well, the OTDR needs a fiber-coupled laser, for one thing, and a decent TIA. Also as John says, it's a time-domain instrument. A laser ruler
can just be a diode laser with a monitor photodiode, a collimating lens,
a simple TIA and a micro with built-in ADC.
You put a small (1-3 mA) current ramp on the laser, and look at the beat signal coming out of the monitor photodiode. The frequency gives you
the round-trip delay. This sort of laser feedback measurement can be
pretty good if the diode stays reasonably single-mode.
I have no idea how the $16 ones do it, but if I were building one,
that's the first thing I'd try.
On 2025-03-09 19:22, Tom Del Rosso wrote:decent TIA. Also as John says, it's a time-domain instrument. A laser
Phil Hobbs wrote:
Hi, All,
Late last year we did a fast sampler/TDR with nice clean 60 ps edges.
We're gearing up to actually sell them, so I did a short technical
writeup on the design, which may be of interest.
<https://electrooptical.net/News/a-high-performance-time-domain-reflectometer>
Cheers
Phil Hobbs
Why is a LASER ruler that can measure distances in air with 2mm accuracy
$16,
and an OTDR for measuring fiber $600?
Well, the OTDR needs a fiber-coupled laser, for one thing, and a
You put a small (1-3 mA) current ramp on the laser, and look at thebeat signal coming out of the monitor photodiode. The frequency gives
I have no idea how the $16 ones do it, but if I were building one,that's the first thing I'd try.
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