How to make a super fast sampling head?

On Thursday, 10 January 2008 17:57:44 UTC+1, Jan Panteltje wrote:

J Larkin was saying his super sampling head costs 750$.
I was thinking how can you make one yourself, what else is needed?

So, I am trying to see if we can make a sub ns S/H, for equivalent time sampling of TDR signals

I was looking at this thread, interesting stuff

I only need 8 bit resolution and 500ps. Could that be done with a mux and a small storage cap (I can sample in about 1us with the ADC after the S/H)

Cheers

Klaus

 

On Tuesday, 9 April 2019 10:59:06 UTC+2, klaus.k...@gmail.com wrote:

On Thursday, 10 January 2008 17:57:44 UTC+1, Jan Panteltje wrote:
J Larkin was saying his super sampling head costs 750$.
I was thinking how can you make one yourself, what else is needed?

So, I am trying to see if we can make a sub ns S/H, for equivalent time sampling of TDR signals

I was looking at this thread, interesting stuff

I only need 8 bit resolution and 500ps. Could that be done with a mux and a small storage cap (I can sample in about 1us with the ADC after the S/H)

I was also thinking about just feeding the signal into a fast logic IC, and offset shifting the input with a DAC output, so over many cycles and different values of the DAC I can reconstruct the signal

But that requires 256 samples per point (for 8 bit) multiplied by the time resolution (number of samples in the time domain), so that could amount to long acquisition time for a complete signal

Cheers

Klaus

 

[Tom Gardner]

On 09/04/19 10:15, klaus.kragelund@gmail.com wrote:

On Tuesday, 9 April 2019 10:59:06 UTC+2, klaus.k...@gmail.com wrote:
On Thursday, 10 January 2008 17:57:44 UTC+1, Jan Panteltje wrote:
J Larkin was saying his super sampling head costs 750$.
I was thinking how can you make one yourself, what else is needed?

So, I am trying to see if we can make a sub ns S/H, for equivalent time sampling of TDR signals

I was looking at this thread, interesting stuff

I only need 8 bit resolution and 500ps. Could that be done with a mux and a small storage cap (I can sample in about 1us with the ADC after the S/H)


I was also thinking about just feeding the signal into a fast logic IC, and offset shifting the input with a DAC output, so over many cycles and different values of the DAC I can reconstruct the signal

But that requires 256 samples per point (for 8 bit) multiplied by the time resolution (number of samples in the time domain), so that could amount to long acquisition time for a complete signal

He might be able to get away with using a SERDES input
to an FPGA (etc), which would remove the number of samples
in the time domain from the equation.

 

[Johann Klammer]

On 04/09/2019 11:15 AM, klaus.kragelund@gmail.com wrote:

On Tuesday, 9 April 2019 10:59:06 UTC+2, klaus.k...@gmail.com wrote:
On Thursday, 10 January 2008 17:57:44 UTC+1, Jan Panteltje wrote:
J Larkin was saying his super sampling head costs 750$.
I was thinking how can you make one yourself, what else is needed?

So, I am trying to see if we can make a sub ns S/H, for equivalent time sampling of TDR signals

I was looking at this thread, interesting stuff

I only need 8 bit resolution and 500ps. Could that be done with a mux and a small storage cap (I can sample in about 1us with the ADC after the S/H)


I was also thinking about just feeding the signal into a fast logic IC, and offset shifting the input with a DAC output, so over many cycles and different values of the DAC I can reconstruct the signal

But that requires 256 samples per point (for 8 bit) multiplied by the time resolution (number of samples in the time domain), so that could amount to long acquisition time for a complete signal

Cheers

Klaus

The only thing I've ever found on the net w.r.t sampling heads was:

sampling.pdf TEK Sampling Oscilloscope Techniques (basic)
an47fa.pdf High Speed Amplifier Techniques (Jim Williams) there's a sampling bridge in there somewhere...
Tektronix "Sampling Notes"
Circuits_1GHz-samplig-Oscilloscope-Front-End.pdf (Robert Houtmann) Looks like it's from a magazine. contains a complete schematic.

(but most of it is pretty old)

 

[Jeroen Belleman]

Johann Klammer wrote:

On 04/09/2019 11:15 AM, klaus.kragelund@gmail.com wrote:
On Tuesday, 9 April 2019 10:59:06 UTC+2, klaus.k...@gmail.com
wrote:
On Thursday, 10 January 2008 17:57:44 UTC+1, Jan Panteltje
wrote:
J Larkin was saying his super sampling head costs 750$. I
was thinking how can you make one yourself, what else is
needed?
So, I am trying to see if we can make a sub ns S/H, for
equivalent time sampling of TDR signals

I was looking at this thread, interesting stuff

I only need 8 bit resolution and 500ps. Could that be done
with a mux and a small storage cap (I can sample in about 1us
with the ADC after the S/H)

I was also thinking about just feeding the signal into a fast
logic IC, and offset shifting the input with a DAC output, so
over many cycles and different values of the DAC I can
reconstruct the signal

But that requires 256 samples per point (for 8 bit) multiplied
by the time resolution (number of samples in the time domain),
so that could amount to long acquisition time for a complete
signal

Cheers

Klaus


The only thing I've ever found on the net w.r.t sampling heads
was:

sampling.pdf TEK Sampling Oscilloscope Techniques (basic)
an47fa.pdf High Speed Amplifier Techniques (Jim Williams) there's
a sampling bridge in there somewhere... Tektronix "Sampling Notes"
Circuits_1GHz-samplig-Oscilloscope-Front-End.pdf (Robert
Houtmann) Looks like it's from a magazine. contains a complete
schematic.

(but most of it is pretty old)

Some years ago, I did some analysis of the Tektronix S-6 sampler
that may serve as a source of inspiration. This thing has a 30ps
rise time.

See <http://cern.ch/jeroen/S6/S6.shtml>.

The sampling pulse is generated using a step-recovery diode and
a shorted stub transmission line.

Jeroen Belleman

 

[Chris Jones]

On 09/04/2019 19:15, klaus.kragelund@gmail.com wrote:

On Tuesday, 9 April 2019 10:59:06 UTC+2, klaus.k...@gmail.com wrote:
On Thursday, 10 January 2008 17:57:44 UTC+1, Jan Panteltje wrote:
J Larkin was saying his super sampling head costs 750$.
I was thinking how can you make one yourself, what else is needed?

So, I am trying to see if we can make a sub ns S/H, for equivalent time sampling of TDR signals

I was looking at this thread, interesting stuff

I only need 8 bit resolution and 500ps. Could that be done with a mux and a small storage cap (I can sample in about 1us with the ADC after the S/H)


I was also thinking about just feeding the signal into a fast logic IC, and offset shifting the input with a DAC output, so over many cycles and different values of the DAC I can reconstruct the signal

But that requires 256 samples per point (for 8 bit) multiplied by the time resolution (number of samples in the time domain), so that could amount to long acquisition time for a complete signal

Cheers

Klaus

I suspect that is basically what this one on kickstarter did:
https://www.eevblog.com/forum/testgear/10-ghz-usb-oscilloscope-by-darwin-sabanovic/

I believe he used Hittite comparators at the input.

You may be able to speed up acquisition a lot by guessing the DAC code
for one timepoint on the waveform, based on the DAC code that you found
for the previous timepoint on the waveform. You'd just have to check 2
DAC codes for a timepoint if you guess right. If it is above one and
below the other then you got it.

On the other hand, I suspect that with noise and jitter, it might be
more a matter of finding the DAC code that gives a 50% probability of
the comparator output being high, which might slow things down much
more. If you spend a really long time you could even characterise the
probability of the comparator output being high vs. DAC code, for each
timepoint.

 

[John Larkin]

On Tue, 9 Apr 2019 23:00:35 +1000, Chris Jones
<lugnut808@spam.yahoo.com> wrote:

On 09/04/2019 19:15, klaus.kragelund@gmail.com wrote:
On Tuesday, 9 April 2019 10:59:06 UTC+2, klaus.k...@gmail.com wrote:
On Thursday, 10 January 2008 17:57:44 UTC+1, Jan Panteltje wrote:
J Larkin was saying his super sampling head costs 750$.
I was thinking how can you make one yourself, what else is needed?

So, I am trying to see if we can make a sub ns S/H, for equivalent time sampling of TDR signals

I was looking at this thread, interesting stuff

I only need 8 bit resolution and 500ps. Could that be done with a mux and a small storage cap (I can sample in about 1us with the ADC after the S/H)


I was also thinking about just feeding the signal into a fast logic IC, and offset shifting the input with a DAC output, so over many cycles and different values of the DAC I can reconstruct the signal

But that requires 256 samples per point (for 8 bit) multiplied by the time resolution (number of samples in the time domain), so that could amount to long acquisition time for a complete signal

Cheers

Klaus

I suspect that is basically what this one on kickstarter did:
https://www.eevblog.com/forum/testgear/10-ghz-usb-oscilloscope-by-darwin-sabanovic/

I believe he used Hittite comparators at the input.

You may be able to speed up acquisition a lot by guessing the DAC code
for one timepoint on the waveform, based on the DAC code that you found
for the previous timepoint on the waveform. You'd just have to check 2
DAC codes for a timepoint if you guess right. If it is above one and
below the other then you got it.

On the other hand, I suspect that with noise and jitter, it might be
more a matter of finding the DAC code that gives a 50% probability of
the comparator output being high, which might slow things down much
more. If you spend a really long time you could even characterise the
probability of the comparator output being high vs. DAC code, for each
timepoint.

Right. Use a tracking algorithm; jog the feedback based on the last,
or maybe last two, binary decisions.


--

John Larkin Highland Technology, Inc

lunatic fringe electronics

 

[John Larkin]

On Tue, 9 Apr 2019 02:15:08 -0700 (PDT), klaus.kragelund@gmail.com
wrote:

On Tuesday, 9 April 2019 10:59:06 UTC+2, klaus.k...@gmail.com wrote:
On Thursday, 10 January 2008 17:57:44 UTC+1, Jan Panteltje wrote:
J Larkin was saying his super sampling head costs 750$.
I was thinking how can you make one yourself, what else is needed?

So, I am trying to see if we can make a sub ns S/H, for equivalent time sampling of TDR signals

I was looking at this thread, interesting stuff

I only need 8 bit resolution and 500ps. Could that be done with a mux and a small storage cap (I can sample in about 1us with the ADC after the S/H)


I was also thinking about just feeding the signal into a fast logic IC, and offset shifting the input with a DAC output, so over many cycles and different values of the DAC I can reconstruct the signal

But that requires 256 samples per point (for 8 bit) multiplied by the time resolution (number of samples in the time domain), so that could amount to long acquisition time for a complete signal

Cheers

Klaus

Right. You can use a d-flop as a 1-bit sampler. The differential-D ECL
parts are expensive but blinding fast. You could use a 15 cent Tiny
CMOS flop to get to your speed.

https://www.dropbox.com/s/unqc6sew8rl4r6u/Binary%20Sampler.gif?dl=0

The feedback algorithm can be linear per shot, so it becomes slew-rate
limited in the equivalent-time domain. That's easier and less noisy
than a binary search. There is some delta-sigma algo that might be
better.

I actually have a pcb layout for a very fast 1-bit TDR/sampler, but I
haven't had time to set it up and play with it.

A full-bridge or better yet 2-diode half-bridge sampler isn't hard.
Typically one closes a diode bias feedback loop so the circuit is
sampling the difference from the last sample. I did that with an SRD
sample generator and got 70 pS, about 5 GHz bandwidth.

https://www.dropbox.com/s/f4ijxsehx8bub5l/Sampler1.JPG?dl=0

At 500 ps, you could make a series switch s/h with a phemt, SAV551
maybe.

I've experimented with fast bus-switch type analog mux's. Their signal
paths are screaming fast, but their switch controls are slow and have
gobs of charge injection. Useless.

Certain barbarians here have done 1-diode Lumatron type samplers,
which Tektronix gave up after the type N plugin and HP never bothered
with. LeCroy later gave that up with shock line technology.

Here's Mark Kahr's great paper on sampling history.

https://www.dropbox.com/s/y6tp7jdga7r0u0u/MarkMTT.pdf?dl=0

and a Tek thing

https://www.dropbox.com/s/ktd077lbubggob3/TekSamplingCircuits.pdf?dl=0



--

John Larkin Highland Technology, Inc

lunatic fringe electronics

 

On Tuesday, 9 April 2019 16:26:26 UTC+2, John Larkin wrote:

On Tue, 9 Apr 2019 02:15:08 -0700 (PDT), klaus.kragelund@gmail.com
wrote:

On Tuesday, 9 April 2019 10:59:06 UTC+2, klaus.k...@gmail.com wrote:
On Thursday, 10 January 2008 17:57:44 UTC+1, Jan Panteltje wrote:
J Larkin was saying his super sampling head costs 750$.
I was thinking how can you make one yourself, what else is needed?

So, I am trying to see if we can make a sub ns S/H, for equivalent time sampling of TDR signals

I was looking at this thread, interesting stuff

I only need 8 bit resolution and 500ps. Could that be done with a mux and a small storage cap (I can sample in about 1us with the ADC after the S/H)


I was also thinking about just feeding the signal into a fast logic IC, and offset shifting the input with a DAC output, so over many cycles and different values of the DAC I can reconstruct the signal

But that requires 256 samples per point (for 8 bit) multiplied by the time resolution (number of samples in the time domain), so that could amount to long acquisition time for a complete signal

Cheers

Klaus

Right. You can use a d-flop as a 1-bit sampler. The differential-D ECL
parts are expensive but blinding fast. You could use a 15 cent Tiny
CMOS flop to get to your speed.

https://www.dropbox.com/s/unqc6sew8rl4r6u/Binary%20Sampler.gif?dl=0

The feedback algorithm can be linear per shot, so it becomes slew-rate
limited in the equivalent-time domain. That's easier and less noisy
than a binary search. There is some delta-sigma algo that might be
better.

I actually have a pcb layout for a very fast 1-bit TDR/sampler, but I
haven't had time to set it up and play with it.

A full-bridge or better yet 2-diode half-bridge sampler isn't hard.
Typically one closes a diode bias feedback loop so the circuit is
sampling the difference from the last sample. I did that with an SRD
sample generator and got 70 pS, about 5 GHz bandwidth.

https://www.dropbox.com/s/f4ijxsehx8bub5l/Sampler1.JPG?dl=0

At 500 ps, you could make a series switch s/h with a phemt, SAV551
maybe.

I've experimented with fast bus-switch type analog mux's. Their signal
paths are screaming fast, but their switch controls are slow and have
gobs of charge injection. Useless.

Certain barbarians here have done 1-diode Lumatron type samplers,
which Tektronix gave up after the type N plugin and HP never bothered
with. LeCroy later gave that up with shock line technology.

Here's Mark Kahr's great paper on sampling history.

https://www.dropbox.com/s/y6tp7jdga7r0u0u/MarkMTT.pdf?dl=0

and a Tek thing

https://www.dropbox.com/s/ktd077lbubggob3/TekSamplingCircuits.pdf?dl=0

Nice set of links

I need to reserve some time to dig into it. Plenty of uses for a high speed S/H, where others would use a brute force GSa ADC.

Cheers

Klaus

 

[John Larkin]

On Tue, 9 Apr 2019 13:57:21 -0700 (PDT), klaus.kragelund@gmail.com
wrote:

On Tuesday, 9 April 2019 16:26:26 UTC+2, John Larkin wrote:
On Tue, 9 Apr 2019 02:15:08 -0700 (PDT), klaus.kragelund@gmail.com
wrote:

On Tuesday, 9 April 2019 10:59:06 UTC+2, klaus.k...@gmail.com wrote:
On Thursday, 10 January 2008 17:57:44 UTC+1, Jan Panteltje wrote:
J Larkin was saying his super sampling head costs 750$.
I was thinking how can you make one yourself, what else is needed?

So, I am trying to see if we can make a sub ns S/H, for equivalent time sampling of TDR signals

I was looking at this thread, interesting stuff

I only need 8 bit resolution and 500ps. Could that be done with a mux and a small storage cap (I can sample in about 1us with the ADC after the S/H)


I was also thinking about just feeding the signal into a fast logic IC, and offset shifting the input with a DAC output, so over many cycles and different values of the DAC I can reconstruct the signal

But that requires 256 samples per point (for 8 bit) multiplied by the time resolution (number of samples in the time domain), so that could amount to long acquisition time for a complete signal

Cheers

Klaus

Right. You can use a d-flop as a 1-bit sampler. The differential-D ECL
parts are expensive but blinding fast. You could use a 15 cent Tiny
CMOS flop to get to your speed.

https://www.dropbox.com/s/unqc6sew8rl4r6u/Binary%20Sampler.gif?dl=0

The feedback algorithm can be linear per shot, so it becomes slew-rate
limited in the equivalent-time domain. That's easier and less noisy
than a binary search. There is some delta-sigma algo that might be
better.

I actually have a pcb layout for a very fast 1-bit TDR/sampler, but I
haven't had time to set it up and play with it.

A full-bridge or better yet 2-diode half-bridge sampler isn't hard.
Typically one closes a diode bias feedback loop so the circuit is
sampling the difference from the last sample. I did that with an SRD
sample generator and got 70 pS, about 5 GHz bandwidth.

https://www.dropbox.com/s/f4ijxsehx8bub5l/Sampler1.JPG?dl=0

At 500 ps, you could make a series switch s/h with a phemt, SAV551
maybe.

I've experimented with fast bus-switch type analog mux's. Their signal
paths are screaming fast, but their switch controls are slow and have
gobs of charge injection. Useless.

Certain barbarians here have done 1-diode Lumatron type samplers,
which Tektronix gave up after the type N plugin and HP never bothered
with. LeCroy later gave that up with shock line technology.

Here's Mark Kahr's great paper on sampling history.

https://www.dropbox.com/s/y6tp7jdga7r0u0u/MarkMTT.pdf?dl=0

and a Tek thing

https://www.dropbox.com/s/ktd077lbubggob3/TekSamplingCircuits.pdf?dl=0

Nice set of links

I need to reserve some time to dig into it. Plenty of uses for a high speed S/H, where others would use a brute force GSa ADC.

Cheers

Klaus

Sampling is fascinating and addictive. But cheap ADCs can have
insanely fast internal s/h circuits.

People used to sell integrated s/h circuits, not so many now.

Some of the Tiny flip-flops have couple-hundred-ps output edges on Q
and Qbar. The pair could drive a full-bridge diode s/h. Maybe $1 or so
total.

A flop is about the only way to get a nicely time aligned
complementary logic pair. Possibly use a pair of 1 ns Tiny xor gates.




--

John Larkin Highland Technology, Inc
picosecond timing precision measurement

jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com

 

[Clifford Heath]

On 10/4/19 9:01 am, John Larkin wrote:

Some of the Tiny flip-flops have couple-hundred-ps output edges on Q
and Qbar. The pair could drive a full-bridge diode s/h. Maybe $1 or so
total.
A flop is about the only way to get a nicely time aligned
complementary logic pair. Possibly use a pair of 1 ns Tiny xor gates.

Isn't it a problem that the pull-up and pull-down are slightly different
Tpd and strength?

Why not a 1:1:1 transformer?

Clifford Heath.

 

[Mike]

On 4/9/2019 1:59 AM, klaus.kragelund@gmail.com wrote:

On Thursday, 10 January 2008 17:57:44 UTC+1, Jan Panteltje wrote:
J Larkin was saying his super sampling head costs 750$.
I was thinking how can you make one yourself, what else is needed?

So, I am trying to see if we can make a sub ns S/H, for equivalent time sampling of TDR signals

I was looking at this thread, interesting stuff

I only need 8 bit resolution and 500ps. Could that be done with a mux and a small storage cap (I can sample in about 1us with the ADC after the S/H)

Cheers

Klaus

Concept is trivial, but the devil is in the details.
For equivalent time sampling, you need a VERY STABLE signal.
You need a DEAD-ON trigger repeatability.
You need to be able to slew the delay between trigger and sample
a very tiny fraction of the period with HIGH accuracy.
Doesn't take much noise to blow all that out of the water.

If all you ever want to do is TDR, it becomes much simpler, but still
not trivial.

https://www.liberatedmanuals.com/TM-9-4935-601-14-3-and-P.pdf

Start with that and convert some of the ancient technology to current stuff.
But much of the magic is in the analog parts.
You don't hear much about blowby compensation, but you'll likely need it.

 

[John Larkin]

On Wed, 10 Apr 2019 00:28:20 -0700, Mike <ham789@netscape.net> wrote:

On 4/9/2019 1:59 AM, klaus.kragelund@gmail.com wrote:
On Thursday, 10 January 2008 17:57:44 UTC+1, Jan Panteltje wrote:
J Larkin was saying his super sampling head costs 750$.
I was thinking how can you make one yourself, what else is needed?

So, I am trying to see if we can make a sub ns S/H, for equivalent time sampling of TDR signals

I was looking at this thread, interesting stuff

I only need 8 bit resolution and 500ps. Could that be done with a mux and a small storage cap (I can sample in about 1us with the ADC after the S/H)

Cheers

Klaus

Concept is trivial, but the devil is in the details.
For equivalent time sampling, you need a VERY STABLE signal.
You need a DEAD-ON trigger repeatability.
You need to be able to slew the delay between trigger and sample
a very tiny fraction of the period with HIGH accuracy.
Doesn't take much noise to blow all that out of the water.

If all you ever want to do is TDR, it becomes much simpler, but still
not trivial.

https://www.liberatedmanuals.com/TM-9-4935-601-14-3-and-P.pdf

Start with that and convert some of the ancient technology to current stuff.
But much of the magic is in the analog parts.
You don't hear much about blowby compensation, but you'll likely need it.

Nowadays, an analog ramp timebase isn't hard. Trigger hits a flop that
releases an RC ramp, which drives a comparator working against a DAC
to set the delay. You can do the whole thing, except the DAC delay
setter, for about a dollar. With just a little care, the RMS jitter
can be 1/10000 of the ramp time; 1/50000 if you are more careful.

Triggered, long-duration, low jitter time bases are a project, as in 1
part in 1e9 jitter. Or 1e12.

TDR has the advantage that your own local clock is the trigger, so you
can get the big chunks of delay by just counting clock ticks.

One thing you can do nowadays is digitally process fast but ugly step
responses to make faster and beautiful step responses. It's a lot
easier to make an ugly sampler or TDR than a pretty one.


--

John Larkin Highland Technology, Inc

lunatic fringe electronics

 

[Hul Tytus]

Klaus - take a look at Electronic Design, Sept 18 2000. The article in
"Ideas for Design", "1-Ghz Sampling Oscilloscope Front end is easily
modified" shows a couble diode swithches setup as a sampler. A couple text
quotes if the titles don't work: "adjustable from 1 to 50 ns/div." and
"circuit by switching the two Schottky".

Hul


klaus.kragelund@gmail.com wrote:

On Thursday, 10 January 2008 17:57:44 UTC+1, Jan Panteltje wrote:
J Larkin was saying his super sampling head costs 750$.
I was thinking how can you make one yourself, what else is needed?

So, I am trying to see if we can make a sub ns S/H, for equivalent time sampling of TDR signals

I was looking at this thread, interesting stuff

I only need 8 bit resolution and 500ps. Could that be done with a mux and a small storage cap (I can sample in about 1us with the ADC after the S/H)

Cheers

Klaus

 

On Wednesday, 10 April 2019 21:13:54 UTC+2, Hul Tytus wrote:

Klaus - take a look at Electronic Design, Sept 18 2000. The article in
"Ideas for Design", "1-Ghz Sampling Oscilloscope Front end is easily
modified" shows a couble diode swithches setup as a sampler. A couple text
quotes if the titles don't work: "adjustable from 1 to 50 ns/div." and
"circuit by switching the two Schottky".

Hul


klaus.kragelund@gmail.com wrote:
On Thursday, 10 January 2008 17:57:44 UTC+1, Jan Panteltje wrote:
J Larkin was saying his super sampling head costs 750$.
I was thinking how can you make one yourself, what else is needed?

So, I am trying to see if we can make a sub ns S/H, for equivalent time sampling of TDR signals

I was looking at this thread, interesting stuff

I only need 8 bit resolution and 500ps. Could that be done with a mux and a small storage cap (I can sample in about 1us with the ADC after the S/H)

That is a very nice reference.

I had some trouble finding it, links were broken on Electronic Design, but found somebody that had saved it as a PDF:

http://www.redrok.com/Circuits_1GHz-samplig-Oscilloscope-Front-End.pdf

Then I found a lot of info on this page:

https://www.eevblog.com/forum/projects/diy-ghz-sampling-head-for-lt100mhz-scopes/

Misc info here from another guy:

https://www.dropbox.com/sh/kmdbbjrzofdxmkb/AADKVlHctfqbE8CNwntixXnza?dl=0%27


A 150ps pulse widht circuit, extremely simple, for TDR generation and sampling:

https://www.eevblog.com/forum/projects/pulse-generator-150ps-1vpp/

Explanation here:

https://www.adv-radio-sci.net/2/7/2004/ars-2-7-2004.pdf


Cheers

Klaus

 

[John Larkin]

On Thu, 11 Apr 2019 23:21:27 -0700 (PDT), klaus.kragelund@gmail.com
wrote:

On Wednesday, 10 April 2019 21:13:54 UTC+2, Hul Tytus wrote:
Klaus - take a look at Electronic Design, Sept 18 2000. The article in
"Ideas for Design", "1-Ghz Sampling Oscilloscope Front end is easily
modified" shows a couble diode swithches setup as a sampler. A couple text
quotes if the titles don't work: "adjustable from 1 to 50 ns/div." and
"circuit by switching the two Schottky".

Hul


klaus.kragelund@gmail.com wrote:
On Thursday, 10 January 2008 17:57:44 UTC+1, Jan Panteltje wrote:
J Larkin was saying his super sampling head costs 750$.
I was thinking how can you make one yourself, what else is needed?

So, I am trying to see if we can make a sub ns S/H, for equivalent time sampling of TDR signals

I was looking at this thread, interesting stuff

I only need 8 bit resolution and 500ps. Could that be done with a mux and a small storage cap (I can sample in about 1us with the ADC after the S/H)


That is a very nice reference.

I had some trouble finding it, links were broken on Electronic Design, but found somebody that had saved it as a PDF:

http://www.redrok.com/Circuits_1GHz-samplig-Oscilloscope-Front-End.pdf

Then I found a lot of info on this page:

https://www.eevblog.com/forum/projects/diy-ghz-sampling-head-for-lt100mhz-scopes/

Misc info here from another guy:

https://www.dropbox.com/sh/kmdbbjrzofdxmkb/AADKVlHctfqbE8CNwntixXnza?dl=0%27


A 150ps pulse widht circuit, extremely simple, for TDR generation and sampling:

https://www.eevblog.com/forum/projects/pulse-generator-150ps-1vpp/

Explanation here:

https://www.adv-radio-sci.net/2/7/2004/ars-2-7-2004.pdf


Cheers

Klaus

Take a look at the TI ONET1xxx laser drivers. Cheap and really fast.


--

John Larkin Highland Technology, Inc

lunatic fringe electronics

 

[Phil Hobbs]

On 4/12/19 11:03 AM, John Larkin wrote:

On Thu, 11 Apr 2019 23:21:27 -0700 (PDT), klaus.kragelund@gmail.com
wrote:

On Wednesday, 10 April 2019 21:13:54 UTC+2, Hul Tytus wrote:
Klaus - take a look at Electronic Design, Sept 18 2000. The article in
"Ideas for Design", "1-Ghz Sampling Oscilloscope Front end is easily
modified" shows a couble diode swithches setup as a sampler. A couple text
quotes if the titles don't work: "adjustable from 1 to 50 ns/div." and
"circuit by switching the two Schottky".

Hul


klaus.kragelund@gmail.com wrote:
On Thursday, 10 January 2008 17:57:44 UTC+1, Jan Panteltje wrote:
J Larkin was saying his super sampling head costs 750$.
I was thinking how can you make one yourself, what else is needed?

So, I am trying to see if we can make a sub ns S/H, for equivalent time sampling of TDR signals

I was looking at this thread, interesting stuff

I only need 8 bit resolution and 500ps. Could that be done with a mux and a small storage cap (I can sample in about 1us with the ADC after the S/H)


That is a very nice reference.

I had some trouble finding it, links were broken on Electronic Design, but found somebody that had saved it as a PDF:

http://www.redrok.com/Circuits_1GHz-samplig-Oscilloscope-Front-End.pdf

Then I found a lot of info on this page:

https://www.eevblog.com/forum/projects/diy-ghz-sampling-head-for-lt100mhz-scopes/

Misc info here from another guy:

https://www.dropbox.com/sh/kmdbbjrzofdxmkb/AADKVlHctfqbE8CNwntixXnza?dl=0%27


A 150ps pulse widht circuit, extremely simple, for TDR generation and sampling:

https://www.eevblog.com/forum/projects/pulse-generator-150ps-1vpp/

Explanation here:

https://www.adv-radio-sci.net/2/7/2004/ars-2-7-2004.pdf


Cheers

Klaus

Take a look at the TI ONET1xxx laser drivers. Cheap and really fast.


25 ps edges and 0.5 ps random jitter. Pretty cool.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics
Optics, Electro-optics, Photonics, Analog Electronics
Briarcliff Manor NY 10510

http://electrooptical.net
http://hobbs-eo.com

 

[John Larkin]

On Fri, 12 Apr 2019 15:36:02 -0400, Phil Hobbs
<pcdhSpamMeSenseless@electrooptical.net> wrote:

On 4/12/19 11:03 AM, John Larkin wrote:
On Thu, 11 Apr 2019 23:21:27 -0700 (PDT), klaus.kragelund@gmail.com
wrote:

On Wednesday, 10 April 2019 21:13:54 UTC+2, Hul Tytus wrote:
Klaus - take a look at Electronic Design, Sept 18 2000. The article in
"Ideas for Design", "1-Ghz Sampling Oscilloscope Front end is easily
modified" shows a couble diode swithches setup as a sampler. A couple text
quotes if the titles don't work: "adjustable from 1 to 50 ns/div." and
"circuit by switching the two Schottky".

Hul


klaus.kragelund@gmail.com wrote:
On Thursday, 10 January 2008 17:57:44 UTC+1, Jan Panteltje wrote:
J Larkin was saying his super sampling head costs 750$.
I was thinking how can you make one yourself, what else is needed?

So, I am trying to see if we can make a sub ns S/H, for equivalent time sampling of TDR signals

I was looking at this thread, interesting stuff

I only need 8 bit resolution and 500ps. Could that be done with a mux and a small storage cap (I can sample in about 1us with the ADC after the S/H)


That is a very nice reference.

I had some trouble finding it, links were broken on Electronic Design, but found somebody that had saved it as a PDF:

http://www.redrok.com/Circuits_1GHz-samplig-Oscilloscope-Front-End.pdf

Then I found a lot of info on this page:

https://www.eevblog.com/forum/projects/diy-ghz-sampling-head-for-lt100mhz-scopes/

Misc info here from another guy:

https://www.dropbox.com/sh/kmdbbjrzofdxmkb/AADKVlHctfqbE8CNwntixXnza?dl=0%27


A 150ps pulse widht circuit, extremely simple, for TDR generation and sampling:

https://www.eevblog.com/forum/projects/pulse-generator-150ps-1vpp/

Explanation here:

https://www.adv-radio-sci.net/2/7/2004/ars-2-7-2004.pdf


Cheers

Klaus

Take a look at the TI ONET1xxx laser drivers. Cheap and really fast.


25 ps edges and 0.5 ps random jitter. Pretty cool.

Cheers

Phil Hobbs

Of course the data sheets assume telecom applications, namely an
ac-coupled, dc-balanced data stream. We're trying to figure if they
can be used DC-coupled.


--

John Larkin Highland Technology, Inc
picosecond timing precision measurement

jlarkin att highlandtechnology dott com
http://www.highlandtechnology.com

 

[Gerhard Hoffmann]

Am 13.04.19 um 00:19 schrieb John Larkin:

Take a look at the TI ONET1xxx laser drivers. Cheap and really fast.


25 ps edges and 0.5 ps random jitter. Pretty cool.

Cheers

Phil Hobbs

Of course the data sheets assume telecom applications, namely an
ac-coupled, dc-balanced data stream. We're trying to figure if they
can be used DC-coupled.

.... and telecom usually ignores the bottom 12 KHz for jitter. Life is
easy without 1/f.

cheers, Gerhard

 

On Friday, 12 April 2019 08:21:31 UTC+2, klaus.k...@gmail.com wrote:

On Wednesday, 10 April 2019 21:13:54 UTC+2, Hul Tytus wrote:
Klaus - take a look at Electronic Design, Sept 18 2000. The article in
"Ideas for Design", "1-Ghz Sampling Oscilloscope Front end is easily
modified" shows a couble diode swithches setup as a sampler. A couple text
quotes if the titles don't work: "adjustable from 1 to 50 ns/div." and
"circuit by switching the two Schottky".

Hul


klaus.kragelund@gmail.com wrote:
On Thursday, 10 January 2008 17:57:44 UTC+1, Jan Panteltje wrote:
J Larkin was saying his super sampling head costs 750$.
I was thinking how can you make one yourself, what else is needed?

So, I am trying to see if we can make a sub ns S/H, for equivalent time sampling of TDR signals

I was looking at this thread, interesting stuff

I only need 8 bit resolution and 500ps. Could that be done with a mux and a small storage cap (I can sample in about 1us with the ADC after the S/H)


That is a very nice reference.

I had some trouble finding it, links were broken on Electronic Design, but found somebody that had saved it as a PDF:

http://www.redrok.com/Circuits_1GHz-samplig-Oscilloscope-Front-End.pdf

Then I found a lot of info on this page:

https://www.eevblog.com/forum/projects/diy-ghz-sampling-head-for-lt100mhz-scopes/

Misc info here from another guy:

https://www.dropbox.com/sh/kmdbbjrzofdxmkb/AADKVlHctfqbE8CNwntixXnza?dl=0%27


A 150ps pulse widht circuit, extremely simple, for TDR generation and sampling:

https://www.eevblog.com/forum/projects/pulse-generator-150ps-1vpp/

Explanation here:

https://www.adv-radio-sci.net/2/7/2004/ars-2-7-2004.pdf


Cheers

Klaus

So, I am plying a little with the sampler from this article i Pspice:

http://www.redrok.com/Circuits_1GHz-samplig-Oscilloscope-Front-End.pdf

It can track a signal resonable, but when the 1ns comparator turns the sample head on (first quad diodes), som charge spills through giving an incorrect amplitude

It's worse when the sampler turns off, on a 1V signal, the amplitude is 100mV off. I am using a small capacitor of 20pF to hold the signal, but the charge transfer from the 2pF shunt capacitance of the diode versus this 20pF cap is too high

If I increase the cap, it's nowhere near a 1GHz sampler, if I decrease it, it has very low hold time

I do not have the 15MOhm/1MOhm - 1pF/15pF (internal cap of TL082) combination, but perhaps I should??

Cheers

Klaus