Super fast sample & hold under $10?

[John Larkin]

On Fri, 07 Feb 2014 09:59:10 -0800, Joerg <invalid@invalid.invalid> wrote:

John Larkin wrote:
On Fri, 07 Feb 2014 07:53:59 -0800, Joerg <invalid@invalid.invalid> wrote:

John Larkin wrote:
On Fri, 07 Feb 2014 18:02:08 +1100, Chris Jones <lugnut808@spam.yahoo.com
wrote:

On 07/02/2014 15:32, John Larkin wrote:
On Thu, 06 Feb 2014 10:32:17 -0800, Joerg <invalid@invalid.invalid> wrote:

John Larkin wrote:
On Thu, 06 Feb 2014 07:55:31 -0800, Joerg <invalid@invalid.invalid> wrote:

John Larkin wrote:
On Thu, 6 Feb 2014 01:08:51 -0500, "Tom Miller" <tmiller11147@verizon.net
wrote:

"John Larkin" <jjlarkin@highNOTlandTHIStechnologyPART.com> wrote in message
news:h496f9lnspapejoj41btps9ebihu2qnk52@4ax.com...
On Wed, 05 Feb 2014 13:01:54 -0800, Joerg <invalid@invalid.invalid> wrote:

Folks,

Need to sample stuff again. Essentially an equivalent time deal like on
older generation digital scopes where you have a 20MHz or so ADC and
GHZ-bandwidth on the scope. Can take as long as it has to but ... the
sampling must be accurate and the sample gate should ideally close and
open in a few hundred picosends, 1nsec at the most. So far I've always
done this stuff in discretes, diode quads, brute-force driver, the
usual. But this gets old and now I need something small and cheap.

Aren't there any ICs in that domain or am I the only one with such
desires?

Also looking for a timer chip to run this but that's easier.
Some ADCs have screaming fast multi-GHz front-end s/h speeds, intended for
sub-Nyquist sampling of RF stuff. 1 ns isn't especially fast in that
world.


--

John Larkin Highland Technology Inc
For $10 ? Put me down for one.

Tom
AD9204-20 has 700 MHz s/h bw, maybe 500 ps, $5.

But when looking at the fine print in here ...

http://www.analog.com/static/imported-files/data_sheets/AD9204.pdf

... it says quote "The user can sample any fs/2 frequency segment from
dc to 200 MHz". Something doesn't seem to compute with the data on page
7 where the fastest version (AD9204-80) still requires 6.25nsec high
phase for the clock. The -20 is 25nsec. How can they do 625MHz with that?
The data sheet is a tad ambiguous about what that 700 MHz thing means.

The min clock pulse width kind of gives it away. I don't think the
sampler could possible be fast enough with that. It'll integrate over
many nsec and that totally spoils the soup here.

I'll put you down for two.

Do you know any cheap one that's faster? I sure wish that instead of all
the no-connect pins they'd pipe out the analog output of the S&H so
people could use it sans the ADC section.
The s/h may not actually exist as such inside.

That could be a problem unless there is a true flash ADC inside.

Do you need a s/h alone, or could you use an adc with a fast s/h inside? There
are probably more ads with fast front ends... I just nabbed that one as an
example.

I don't quite understand the application.

This one I really can't talk about but essentially I need to be able to
digitize a very high frequency event in an equivalent time fashion, like
on old DSOs. Or very fast new ones. A very fast ADC is far from ideal
here but could work if nothing else is there. And it seems there ain't.


Could you use a diode mixer and a narrow pulse generator? That could be cheap.

Yes, but diodes still have almost a pF when operated as quads, even the
fancy Skyworks ones. Too much leakage when off. The only way to make
that work would be a slew of T-configuration sections. Gets big and
expensive. In an IC that would be easy to do but there seems to be not
enough market. There are some boutique chips but those cost hundreds of
Dollars.
There is the 1-bit sampler thing, namely using a d-flop as an equivalent-time
sampler, sort of a tracking ADC. It takes a lot of samples to build the
waveform, but it's potentially cheap. A differential-input D flop, like an
EL/EP52, can do that.


Yes, well I had always thought of doing it with a clocked comparator
like the ADCMP572 etc., and the other input connected to a slow DAC. The
tricky part is generating the clock pulse to the comparator, with
accurately variable timing relative to the trigger input, but this might
be easy if you control the stimulus to the circuit.

Another guy seems to have also thought of it:
https://www.kickstarter.com/projects/1855991221/10-ghz-usb-oscilloscope
though he says the Hittite comparators are faster than the ADI ones.

Chris
I did it with tunnel diodes in 1969, inspired by a circuit in the GE Transistor
Manual.

The advantage of the EL flop is that it's within Joerg's budget. ...

It could do it but it would be a potentially long iterative process per
sample time slot. An option may be to use some clever seek method
instead of a stair-step ramp. Go to full, if not there go to half. If
there go to 3/4, if not there go to 1/4, and so on. In my case the
computational overhead would jinx it though.


You can do a feedback loop on the go/nogo decisions of the comparator/flipflop,
so the thing becomes a tracking ADC of sorts. That's not too awful if the
equivalent-time sweep is fairly slow.

If the clock rate is constant, the feedback loop could be just an RC or RLC from
Q to \D, something like that.


Might be an option, I'll have to think that through. The sweep time is
several hundred times the sampling window and can be made constant.

An EL52 has differential D and clock inputs. The D input becomes the signal to
be sampled and the slow feedback. The diff clock input can be the
equivalent-time ramp timebase comparator.

Not bad for one 8-pin part.


--

John Larkin Highland Technology Inc
www.highlandtechnology.com jlarkin at highlandtechnology dot com

Precision electronic instrumentation

 

[John Larkin]

On Fri, 07 Feb 2014 17:55:29 -0800, Joerg <invalid@invalid.invalid> wrote:

John Larkin wrote:
On Fri, 07 Feb 2014 09:59:10 -0800, Joerg <invalid@invalid.invalid> wrote:

John Larkin wrote:
On Fri, 07 Feb 2014 07:53:59 -0800, Joerg <invalid@invalid.invalid> wrote:

John Larkin wrote:
On Fri, 07 Feb 2014 18:02:08 +1100, Chris Jones <lugnut808@spam.yahoo.com
wrote:

On 07/02/2014 15:32, John Larkin wrote:
On Thu, 06 Feb 2014 10:32:17 -0800, Joerg <invalid@invalid.invalid> wrote:

John Larkin wrote:
On Thu, 06 Feb 2014 07:55:31 -0800, Joerg <invalid@invalid.invalid> wrote:

John Larkin wrote:
On Thu, 6 Feb 2014 01:08:51 -0500, "Tom Miller" <tmiller11147@verizon.net
wrote:

"John Larkin" <jjlarkin@highNOTlandTHIStechnologyPART.com> wrote in message
news:h496f9lnspapejoj41btps9ebihu2qnk52@4ax.com...
On Wed, 05 Feb 2014 13:01:54 -0800, Joerg <invalid@invalid.invalid> wrote:

Folks,

Need to sample stuff again. Essentially an equivalent time deal like on
older generation digital scopes where you have a 20MHz or so ADC and
GHZ-bandwidth on the scope. Can take as long as it has to but ... the
sampling must be accurate and the sample gate should ideally close and
open in a few hundred picosends, 1nsec at the most. So far I've always
done this stuff in discretes, diode quads, brute-force driver, the
usual. But this gets old and now I need something small and cheap.

Aren't there any ICs in that domain or am I the only one with such
desires?

Also looking for a timer chip to run this but that's easier.
Some ADCs have screaming fast multi-GHz front-end s/h speeds, intended for
sub-Nyquist sampling of RF stuff. 1 ns isn't especially fast in that
world.


--

John Larkin Highland Technology Inc
For $10 ? Put me down for one.

Tom
AD9204-20 has 700 MHz s/h bw, maybe 500 ps, $5.

But when looking at the fine print in here ...

http://www.analog.com/static/imported-files/data_sheets/AD9204.pdf

... it says quote "The user can sample any fs/2 frequency segment from
dc to 200 MHz". Something doesn't seem to compute with the data on page
7 where the fastest version (AD9204-80) still requires 6.25nsec high
phase for the clock. The -20 is 25nsec. How can they do 625MHz with that?
The data sheet is a tad ambiguous about what that 700 MHz thing means.

The min clock pulse width kind of gives it away. I don't think the
sampler could possible be fast enough with that. It'll integrate over
many nsec and that totally spoils the soup here.

I'll put you down for two.

Do you know any cheap one that's faster? I sure wish that instead of all
the no-connect pins they'd pipe out the analog output of the S&H so
people could use it sans the ADC section.
The s/h may not actually exist as such inside.

That could be a problem unless there is a true flash ADC inside.

Do you need a s/h alone, or could you use an adc with a fast s/h inside? There
are probably more ads with fast front ends... I just nabbed that one as an
example.

I don't quite understand the application.

This one I really can't talk about but essentially I need to be able to
digitize a very high frequency event in an equivalent time fashion, like
on old DSOs. Or very fast new ones. A very fast ADC is far from ideal
here but could work if nothing else is there. And it seems there ain't.


Could you use a diode mixer and a narrow pulse generator? That could be cheap.

Yes, but diodes still have almost a pF when operated as quads, even the
fancy Skyworks ones. Too much leakage when off. The only way to make
that work would be a slew of T-configuration sections. Gets big and
expensive. In an IC that would be easy to do but there seems to be not
enough market. There are some boutique chips but those cost hundreds of
Dollars.
There is the 1-bit sampler thing, namely using a d-flop as an equivalent-time
sampler, sort of a tracking ADC. It takes a lot of samples to build the
waveform, but it's potentially cheap. A differential-input D flop, like an
EL/EP52, can do that.


Yes, well I had always thought of doing it with a clocked comparator
like the ADCMP572 etc., and the other input connected to a slow DAC. The
tricky part is generating the clock pulse to the comparator, with
accurately variable timing relative to the trigger input, but this might
be easy if you control the stimulus to the circuit.

Another guy seems to have also thought of it:
https://www.kickstarter.com/projects/1855991221/10-ghz-usb-oscilloscope
though he says the Hittite comparators are faster than the ADI ones.

Chris
I did it with tunnel diodes in 1969, inspired by a circuit in the GE Transistor
Manual.

The advantage of the EL flop is that it's within Joerg's budget. ...
It could do it but it would be a potentially long iterative process per
sample time slot. An option may be to use some clever seek method
instead of a stair-step ramp. Go to full, if not there go to half. If
there go to 3/4, if not there go to 1/4, and so on. In my case the
computational overhead would jinx it though.

You can do a feedback loop on the go/nogo decisions of the comparator/flipflop,
so the thing becomes a tracking ADC of sorts. That's not too awful if the
equivalent-time sweep is fairly slow.

If the clock rate is constant, the feedback loop could be just an RC or RLC from
Q to \D, something like that.

Might be an option, I'll have to think that through. The sweep time is
several hundred times the sampling window and can be made constant.

An EL52 has differential D and clock inputs. The D input becomes the signal to
be sampled and the slow feedback. The diff clock input can be the
equivalent-time ramp timebase comparator.


However, min pulse width is 400psec which is almost twice of what my
goal is.

http://www.onsemi.com/pub_link/Collateral/MC10EL52-D.PDF

The real question is how fast the front end of the flipflop is. Prop delay after
that doesn't matter.

Use an EP52 to go faster. SiGe.

Not bad for one 8-pin part.


Indeed. They don't go berserk during phases where the two D inputs are
close to each other and barely moving? Most of the time when I did that
with logic chips everything lit up.

Well, you'd have to try it.



--

John Larkin Highland Technology Inc
www.highlandtechnology.com jlarkin at highlandtechnology dot com

Precision electronic instrumentation

 

[Joerg]

John Larkin wrote:

On Fri, 07 Feb 2014 09:59:10 -0800, Joerg <invalid@invalid.invalid> wrote:

John Larkin wrote:
On Fri, 07 Feb 2014 07:53:59 -0800, Joerg <invalid@invalid.invalid> wrote:

John Larkin wrote:
On Fri, 07 Feb 2014 18:02:08 +1100, Chris Jones <lugnut808@spam.yahoo.com
wrote:

On 07/02/2014 15:32, John Larkin wrote:
On Thu, 06 Feb 2014 10:32:17 -0800, Joerg <invalid@invalid.invalid> wrote:

John Larkin wrote:
On Thu, 06 Feb 2014 07:55:31 -0800, Joerg <invalid@invalid.invalid> wrote:

John Larkin wrote:
On Thu, 6 Feb 2014 01:08:51 -0500, "Tom Miller" <tmiller11147@verizon.net
wrote:

"John Larkin" <jjlarkin@highNOTlandTHIStechnologyPART.com> wrote in message
news:h496f9lnspapejoj41btps9ebihu2qnk52@4ax.com...
On Wed, 05 Feb 2014 13:01:54 -0800, Joerg <invalid@invalid.invalid> wrote:

Folks,

Need to sample stuff again. Essentially an equivalent time deal like on
older generation digital scopes where you have a 20MHz or so ADC and
GHZ-bandwidth on the scope. Can take as long as it has to but ... the
sampling must be accurate and the sample gate should ideally close and
open in a few hundred picosends, 1nsec at the most. So far I've always
done this stuff in discretes, diode quads, brute-force driver, the
usual. But this gets old and now I need something small and cheap.

Aren't there any ICs in that domain or am I the only one with such
desires?

Also looking for a timer chip to run this but that's easier.
Some ADCs have screaming fast multi-GHz front-end s/h speeds, intended for
sub-Nyquist sampling of RF stuff. 1 ns isn't especially fast in that
world.


--

John Larkin Highland Technology Inc
For $10 ? Put me down for one.

Tom
AD9204-20 has 700 MHz s/h bw, maybe 500 ps, $5.

But when looking at the fine print in here ...

http://www.analog.com/static/imported-files/data_sheets/AD9204.pdf

... it says quote "The user can sample any fs/2 frequency segment from
dc to 200 MHz". Something doesn't seem to compute with the data on page
7 where the fastest version (AD9204-80) still requires 6.25nsec high
phase for the clock. The -20 is 25nsec. How can they do 625MHz with that?
The data sheet is a tad ambiguous about what that 700 MHz thing means.

The min clock pulse width kind of gives it away. I don't think the
sampler could possible be fast enough with that. It'll integrate over
many nsec and that totally spoils the soup here.

I'll put you down for two.

Do you know any cheap one that's faster? I sure wish that instead of all
the no-connect pins they'd pipe out the analog output of the S&H so
people could use it sans the ADC section.
The s/h may not actually exist as such inside.

That could be a problem unless there is a true flash ADC inside.

Do you need a s/h alone, or could you use an adc with a fast s/h inside? There
are probably more ads with fast front ends... I just nabbed that one as an
example.

I don't quite understand the application.

This one I really can't talk about but essentially I need to be able to
digitize a very high frequency event in an equivalent time fashion, like
on old DSOs. Or very fast new ones. A very fast ADC is far from ideal
here but could work if nothing else is there. And it seems there ain't.


Could you use a diode mixer and a narrow pulse generator? That could be cheap.

Yes, but diodes still have almost a pF when operated as quads, even the
fancy Skyworks ones. Too much leakage when off. The only way to make
that work would be a slew of T-configuration sections. Gets big and
expensive. In an IC that would be easy to do but there seems to be not
enough market. There are some boutique chips but those cost hundreds of
Dollars.
There is the 1-bit sampler thing, namely using a d-flop as an equivalent-time
sampler, sort of a tracking ADC. It takes a lot of samples to build the
waveform, but it's potentially cheap. A differential-input D flop, like an
EL/EP52, can do that.


Yes, well I had always thought of doing it with a clocked comparator
like the ADCMP572 etc., and the other input connected to a slow DAC. The
tricky part is generating the clock pulse to the comparator, with
accurately variable timing relative to the trigger input, but this might
be easy if you control the stimulus to the circuit.

Another guy seems to have also thought of it:
https://www.kickstarter.com/projects/1855991221/10-ghz-usb-oscilloscope
though he says the Hittite comparators are faster than the ADI ones.

Chris
I did it with tunnel diodes in 1969, inspired by a circuit in the GE Transistor
Manual.

The advantage of the EL flop is that it's within Joerg's budget. ...
It could do it but it would be a potentially long iterative process per
sample time slot. An option may be to use some clever seek method
instead of a stair-step ramp. Go to full, if not there go to half. If
there go to 3/4, if not there go to 1/4, and so on. In my case the
computational overhead would jinx it though.

You can do a feedback loop on the go/nogo decisions of the comparator/flipflop,
so the thing becomes a tracking ADC of sorts. That's not too awful if the
equivalent-time sweep is fairly slow.

If the clock rate is constant, the feedback loop could be just an RC or RLC from
Q to \D, something like that.

Might be an option, I'll have to think that through. The sweep time is
several hundred times the sampling window and can be made constant.

An EL52 has differential D and clock inputs. The D input becomes the signal to
be sampled and the slow feedback. The diff clock input can be the
equivalent-time ramp timebase comparator.

However, min pulse width is 400psec which is almost twice of what my
goal is.

http://www.onsemi.com/pub_link/Collateral/MC10EL52-D.PDF

Not bad for one 8-pin part.

Indeed. They don't go berserk during phases where the two D inputs are
close to each other and barely moving? Most of the time when I did that
with logic chips everything lit up.

--
Regards, Joerg

http://www.analogconsultants.com/

 

[josephkk]

On Thu, 06 Feb 2014 14:29:39 -0800, Joerg <invalid@invalid.invalid> wrote:

The procedure, hope nothing is wrong:

Use a micro output or whatever to charge the capacitor on the output of the comparator (node OUT)
Hi-state the micro output (node OUT)
Enable the comparator for 500ps (you need a fast comparator). The comparator slews the output to the input value. When node OUT is equal to the input signal, node OC rises.
When OC rises, use that to Disable the comparator (needs perhaps level translation circuit)
Use the OC rise to trigger the microcontroller to start ADC conversion.


That is a clever method. With comparators there is one problem though:
When a very fast comparator sees little change or too slow a change on
the input side it can burst into oscillation. If it doesn't see
10mV/nsec or more it can go berserk, they are meant more for digital stuff.

Well kind of sorta. Most of their use is in demodulating QAM 8 and
similar signals, relatively yes/no types of stuff. Once upon a time they
were the proper real thing (about 30+ years ago). They weren't nearly as
fast back then either.

?-)

 

[Joerg]

John Larkin wrote:

On Fri, 07 Feb 2014 17:55:29 -0800, Joerg <invalid@invalid.invalid> wrote:

John Larkin wrote:
On Fri, 07 Feb 2014 09:59:10 -0800, Joerg <invalid@invalid.invalid> wrote:

John Larkin wrote:
On Fri, 07 Feb 2014 07:53:59 -0800, Joerg <invalid@invalid.invalid> wrote:

John Larkin wrote:
On Fri, 07 Feb 2014 18:02:08 +1100, Chris Jones <lugnut808@spam.yahoo.com
wrote:

On 07/02/2014 15:32, John Larkin wrote:
On Thu, 06 Feb 2014 10:32:17 -0800, Joerg <invalid@invalid.invalid> wrote:

John Larkin wrote:
On Thu, 06 Feb 2014 07:55:31 -0800, Joerg <invalid@invalid.invalid> wrote:

John Larkin wrote:
On Thu, 6 Feb 2014 01:08:51 -0500, "Tom Miller" <tmiller11147@verizon.net
wrote:

"John Larkin" <jjlarkin@highNOTlandTHIStechnologyPART.com> wrote in message
news:h496f9lnspapejoj41btps9ebihu2qnk52@4ax.com...
On Wed, 05 Feb 2014 13:01:54 -0800, Joerg <invalid@invalid.invalid> wrote:

Folks,

Need to sample stuff again. Essentially an equivalent time deal like on
older generation digital scopes where you have a 20MHz or so ADC and
GHZ-bandwidth on the scope. Can take as long as it has to but ... the
sampling must be accurate and the sample gate should ideally close and
open in a few hundred picosends, 1nsec at the most. So far I've always
done this stuff in discretes, diode quads, brute-force driver, the
usual. But this gets old and now I need something small and cheap.

Aren't there any ICs in that domain or am I the only one with such
desires?

Also looking for a timer chip to run this but that's easier.
Some ADCs have screaming fast multi-GHz front-end s/h speeds, intended for
sub-Nyquist sampling of RF stuff. 1 ns isn't especially fast in that
world.


--

John Larkin Highland Technology Inc
For $10 ? Put me down for one.

Tom
AD9204-20 has 700 MHz s/h bw, maybe 500 ps, $5.

But when looking at the fine print in here ...

http://www.analog.com/static/imported-files/data_sheets/AD9204.pdf

... it says quote "The user can sample any fs/2 frequency segment from
dc to 200 MHz". Something doesn't seem to compute with the data on page
7 where the fastest version (AD9204-80) still requires 6.25nsec high
phase for the clock. The -20 is 25nsec. How can they do 625MHz with that?
The data sheet is a tad ambiguous about what that 700 MHz thing means.

The min clock pulse width kind of gives it away. I don't think the
sampler could possible be fast enough with that. It'll integrate over
many nsec and that totally spoils the soup here.

I'll put you down for two.

Do you know any cheap one that's faster? I sure wish that instead of all
the no-connect pins they'd pipe out the analog output of the S&H so
people could use it sans the ADC section.
The s/h may not actually exist as such inside.

That could be a problem unless there is a true flash ADC inside.

Do you need a s/h alone, or could you use an adc with a fast s/h inside? There
are probably more ads with fast front ends... I just nabbed that one as an
example.

I don't quite understand the application.

This one I really can't talk about but essentially I need to be able to
digitize a very high frequency event in an equivalent time fashion, like
on old DSOs. Or very fast new ones. A very fast ADC is far from ideal
here but could work if nothing else is there. And it seems there ain't.


Could you use a diode mixer and a narrow pulse generator? That could be cheap.

Yes, but diodes still have almost a pF when operated as quads, even the
fancy Skyworks ones. Too much leakage when off. The only way to make
that work would be a slew of T-configuration sections. Gets big and
expensive. In an IC that would be easy to do but there seems to be not
enough market. There are some boutique chips but those cost hundreds of
Dollars.
There is the 1-bit sampler thing, namely using a d-flop as an equivalent-time
sampler, sort of a tracking ADC. It takes a lot of samples to build the
waveform, but it's potentially cheap. A differential-input D flop, like an
EL/EP52, can do that.


Yes, well I had always thought of doing it with a clocked comparator
like the ADCMP572 etc., and the other input connected to a slow DAC. The
tricky part is generating the clock pulse to the comparator, with
accurately variable timing relative to the trigger input, but this might
be easy if you control the stimulus to the circuit.

Another guy seems to have also thought of it:
https://www.kickstarter.com/projects/1855991221/10-ghz-usb-oscilloscope
though he says the Hittite comparators are faster than the ADI ones.

Chris
I did it with tunnel diodes in 1969, inspired by a circuit in the GE Transistor
Manual.

The advantage of the EL flop is that it's within Joerg's budget. ...
It could do it but it would be a potentially long iterative process per
sample time slot. An option may be to use some clever seek method
instead of a stair-step ramp. Go to full, if not there go to half. If
there go to 3/4, if not there go to 1/4, and so on. In my case the
computational overhead would jinx it though.

You can do a feedback loop on the go/nogo decisions of the comparator/flipflop,
so the thing becomes a tracking ADC of sorts. That's not too awful if the
equivalent-time sweep is fairly slow.

If the clock rate is constant, the feedback loop could be just an RC or RLC from
Q to \D, something like that.

Might be an option, I'll have to think that through. The sweep time is
several hundred times the sampling window and can be made constant.
An EL52 has differential D and clock inputs. The D input becomes the signal to
be sampled and the slow feedback. The diff clock input can be the
equivalent-time ramp timebase comparator.

However, min pulse width is 400psec which is almost twice of what my
goal is.

http://www.onsemi.com/pub_link/Collateral/MC10EL52-D.PDF



The real question is how fast the front end of the flipflop is. Prop delay after
that doesn't matter.

Use an EP52 to go faster. SiGe.

4GHz is impresive but it also wants a minimum pulse time, this one even
says 450psec.

http://www.micrel.com/_PDF/HBW/sy10ep52v.pdf

Not bad for one 8-pin part.

Indeed. They don't go berserk during phases where the two D inputs are
close to each other and barely moving? Most of the time when I did that
with logic chips everything lit up.

Well, you'd have to try it.

Yep. If there is enough time I could but it would still be dicey. Seen
too many designs where folks relied on certain undocumented performance
features. Then the mfg built a new foundry, moved the process over, and
.... poof.

Like you I drive FETs and stuff well past their datasheet speeds but
those are fairly staid processes. They are also cheap so even a lifetime
purchase can be feasible. But I've seen a case where someone did that in
the world of optics and suddenly a whole big product line came crashing
down.

--
Regards, Joerg

http://www.analogconsultants.com/

 

[Clifford Heath]

On 06/02/14 12:29, Maynard A. Philbrook Jr. wrote:

In article <lcuftk$npa$1@dont-email.me>,
pcdhSpamMeSenseless@electrooptical.net says...
Well, if you don't mind biasing it yourself, there's the HFA3102.
Phil Hobbs
Or maybe a gilbert cell, any one up for a mixer ?

You want the HFA3101 for that. Same die.

 

[whit3rd]

On Friday, February 7, 2014 5:55:29 PM UTC-8, Joerg wrote:

John Larkin wrote:
[about fast flip/flop]

However, min pulse width is 400psec which is almost twice of what my

goal is.

If you capacitor-couple so one edge puts a current pulse into a gain
cell (I suggested the OPA860) the sampling only lasts as long as
the current pulse. The rest of the 'pulse width' is just deadtime,
which (in most samplers) isn't the big concern.
The OPA860 is a transconductance amplifier, output current is nil
after you turn off its Iq current source. That's the 'hold' part.
And current output is proportional to input voltage times Iq when
the Iq source is on. That's the 'sample' part.
During dead time, you need to both digitize the sampled value, and
discharge the capacitor to some known level. And, reset the flip/flop.

 

[Joerg]

whit3rd wrote:

On Friday, February 7, 2014 5:55:29 PM UTC-8, Joerg wrote:
John Larkin wrote:
[about fast flip/flop]

However, min pulse width is 400psec which is almost twice of what my

goal is.

If you capacitor-couple so one edge puts a current pulse into a gain
cell (I suggested the OPA860) the sampling only lasts as long as
the current pulse. ...

AFAIU that will not working with the flip-flops John suggested because
they are not guaranteed to function with less than 400psec. But who
knows what they do inside, it might work.

... The rest of the 'pulse width' is just deadtime,
which (in most samplers) isn't the big concern.
The OPA860 is a transconductance amplifier, output current is nil
after you turn off its Iq current source. That's the 'hold' part.
And current output is proportional to input voltage times Iq when
the Iq source is on. That's the 'sample' part.
During dead time, you need to both digitize the sampled value, and
discharge the capacitor to some known level. And, reset the flip/flop.

Using it directly to sample the RF could be a stretch because the BW of
the OTA in there is low. But it might be useful as a "post-sampler"
which I'll need because of slow ADC capabilities. The off the shelf S&H
chips are boringly slow. No idea why because I've built much faster ones
in discrete and there was nothing that would have prevented integration
into a chip.

--
Regards, Joerg

http://www.analogconsultants.com/

 

[John Larkin]

On Mon, 10 Feb 2014 10:03:52 -0800, Joerg <invalid@invalid.invalid> wrote:

whit3rd wrote:
On Friday, February 7, 2014 5:55:29 PM UTC-8, Joerg wrote:
John Larkin wrote:
[about fast flip/flop]

However, min pulse width is 400psec which is almost twice of what my

goal is.

If you capacitor-couple so one edge puts a current pulse into a gain
cell (I suggested the OPA860) the sampling only lasts as long as
the current pulse. ...


AFAIU that will not working with the flip-flops John suggested because
they are not guaranteed to function with less than 400psec. But who
knows what they do inside, it might work.

The clock can be very wide; only the rising edge matters. The question is, what
is the effective bandwidth of the latch inside?

This is too good not to try:

https://dl.dropboxusercontent.com/u/53724080/Sampling/Slideback_Sampler.JPG

Sampler and timebase comparator in one chip!



--

John Larkin Highland Technology Inc
www.highlandtechnology.com jlarkin at highlandtechnology dot com

Precision electronic instrumentation

 

[Klaus Kragelund]

On Friday, February 7, 2014 7:31:56 PM UTC+1, John Larkin wrote:

On Fri, 07 Feb 2014 10:04:23 -0800, Joerg <invalid@invalid.invalid

wrote:



John Larkin wrote:

On Wed, 05 Feb 2014 13:01:54 -0800, Joerg <invalid@invalid.invalid> wrote:



Folks,



Need to sample stuff again. Essentially an equivalent time deal like on

older generation digital scopes where you have a 20MHz or so ADC and

GHZ-bandwidth on the scope. Can take as long as it has to but ... the

sampling must be accurate and the sample gate should ideally close and

open in a few hundred picosends, 1nsec at the most. So far I've always

done this stuff in discretes, diode quads, brute-force driver, the

usual. But this gets old and now I need something small and cheap.



Aren't there any ICs in that domain or am I the only one with such desires?



Also looking for a timer chip to run this but that's easier.



The classic sampling-scope circuit can be built cheap. SRD, clip lines, 2-diode

sampler, charge amp.



This got about 5 GHz bandwidth:



https://dl.dropboxusercontent.com/u/53724080/Protos/Sampler1.JPG





I was mulling a 2-diode sampler because then you don't get that 100%

sampling pulse feed-through that you have with single-diode sampling.

But it doubles the capacitance. Doesn't it leak too much?



Schottky diodes don't leak badly. You have to read it out in a few us

after the sample.



There is also "blow-by", which is capacitive feedthrough of the

diodes. That is easily compensated with an opamp.



Sampling efficiency of a fast sampler (the output voltage over the

input voltage) is low, a few per cent maybe, but gain is cheap.



The classic HP 2-diode feedback sampler is well documented.

Is the 2 diode sampler used any more due to the delay of the resistors in this configuration or is it another 2 diode sampler you are referring to?

What would be good mathing diodes for the 4 diode samplers?

Cheers

Klaus

 

[Lasse Langwadt Christense]

Den tirsdag den 11. februar 2014 13.08.54 UTC+1 skrev Klaus Kragelund:

On Friday, February 7, 2014 7:31:56 PM UTC+1, John Larkin wrote:

On Fri, 07 Feb 2014 10:04:23 -0800, Joerg <invalid@invalid.invalid



wrote:







John Larkin wrote:



On Wed, 05 Feb 2014 13:01:54 -0800, Joerg <invalid@invalid.invalid> wrote:







Folks,







Need to sample stuff again. Essentially an equivalent time deal like on



older generation digital scopes where you have a 20MHz or so ADC and



GHZ-bandwidth on the scope. Can take as long as it has to but ... the



sampling must be accurate and the sample gate should ideally close and



open in a few hundred picosends, 1nsec at the most. So far I've always



done this stuff in discretes, diode quads, brute-force driver, the



usual. But this gets old and now I need something small and cheap.







Aren't there any ICs in that domain or am I the only one with such desires?







Also looking for a timer chip to run this but that's easier.







The classic sampling-scope circuit can be built cheap. SRD, clip lines, 2-diode



sampler, charge amp.







This got about 5 GHz bandwidth:







https://dl.dropboxusercontent.com/u/53724080/Protos/Sampler1.JPG











I was mulling a 2-diode sampler because then you don't get that 100%



sampling pulse feed-through that you have with single-diode sampling.



But it doubles the capacitance. Doesn't it leak too much?







Schottky diodes don't leak badly. You have to read it out in a few us



after the sample.







There is also "blow-by", which is capacitive feedthrough of the



diodes. That is easily compensated with an opamp.







Sampling efficiency of a fast sampler (the output voltage over the



input voltage) is low, a few per cent maybe, but gain is cheap.







The classic HP 2-diode feedback sampler is well documented.





Is the 2 diode sampler used any more due to the delay of the resistors in this configuration or is it another 2 diode sampler you are referring to?



What would be good mathing diodes for the 4 diode samplers?

no idea, never had to build sampler only seen it on a schematic

I wonder if those low capacitance ESD array could be used?

say something like CM1230-02CP for a four diode ?


-Lasse

 

[John Larkin]

On Tue, 11 Feb 2014 04:08:54 -0800 (PST), Klaus Kragelund
<klauskvik@hotmail.com> wrote:

On Friday, February 7, 2014 7:31:56 PM UTC+1, John Larkin wrote:
On Fri, 07 Feb 2014 10:04:23 -0800, Joerg <invalid@invalid.invalid

wrote:



John Larkin wrote:

On Wed, 05 Feb 2014 13:01:54 -0800, Joerg <invalid@invalid.invalid> wrote:



Folks,



Need to sample stuff again. Essentially an equivalent time deal like on

older generation digital scopes where you have a 20MHz or so ADC and

GHZ-bandwidth on the scope. Can take as long as it has to but ... the

sampling must be accurate and the sample gate should ideally close and

open in a few hundred picosends, 1nsec at the most. So far I've always

done this stuff in discretes, diode quads, brute-force driver, the

usual. But this gets old and now I need something small and cheap.



Aren't there any ICs in that domain or am I the only one with such desires?



Also looking for a timer chip to run this but that's easier.



The classic sampling-scope circuit can be built cheap. SRD, clip lines, 2-diode

sampler, charge amp.



This got about 5 GHz bandwidth:



https://dl.dropboxusercontent.com/u/53724080/Protos/Sampler1.JPG





I was mulling a 2-diode sampler because then you don't get that 100%

sampling pulse feed-through that you have with single-diode sampling.

But it doubles the capacitance. Doesn't it leak too much?



Schottky diodes don't leak badly. You have to read it out in a few us

after the sample.



There is also "blow-by", which is capacitive feedthrough of the

diodes. That is easily compensated with an opamp.



Sampling efficiency of a fast sampler (the output voltage over the

input voltage) is low, a few per cent maybe, but gain is cheap.



The classic HP 2-diode feedback sampler is well documented.


Is the 2 diode sampler used any more due to the delay of the resistors in this configuration or is it another 2 diode sampler you are referring to?

What would be good mathing diodes for the 4 diode samplers?

Cheers

Klaus

2-diode samplers have been done up to 200 GHz or so. They are monolithic
structures with shock-line sample pulse generators. Google shock line sampler
or something like that.




--

John Larkin Highland Technology Inc
www.highlandtechnology.com jlarkin at highlandtechnology dot com

Precision electronic instrumentation

 

[Joerg]

John Larkin wrote:

On Mon, 10 Feb 2014 10:03:52 -0800, Joerg <invalid@invalid.invalid> wrote:

whit3rd wrote:
On Friday, February 7, 2014 5:55:29 PM UTC-8, Joerg wrote:
John Larkin wrote:
[about fast flip/flop]

However, min pulse width is 400psec which is almost twice of what my

goal is.
If you capacitor-couple so one edge puts a current pulse into a gain
cell (I suggested the OPA860) the sampling only lasts as long as
the current pulse. ...

AFAIU that will not working with the flip-flops John suggested because
they are not guaranteed to function with less than 400psec. But who
knows what they do inside, it might work.

The clock can be very wide; only the rising edge matters. The question is, what
is the effective bandwidth of the latch inside?

Not just that. Also important is what it'll do in the analog range
(inputs very close to each other or nearly identical).

This is too good not to try:

https://dl.dropboxusercontent.com/u/53724080/Sampling/Slideback_Sampler.JPG

Sampler and timebase comparator in one chip!

That is very clever. Wish I could try that but the lowest I can measure
in my lab here is around 500psec.

The risk is oscillation and it happened when I tried something similar,
trying to log time between fast zero crossings. When they became slow or
the signal dropped out the indicated power supply current suddenly
jumped up, big time. The chip became smoking hot, even after I took
everything except the terminators off the output. The onset was always
sudden, indicating internal oscillation although we had no tools back
then to verify emissions in the GHz range. Ok, this was in the days when
Motorola was still Motorola but probably the innards of such ECL chips
haven't changed much other than in the foundry process.

--
Regards, Joerg

http://www.analogconsultants.com/

 

[Joerg]

Klaus Kragelund wrote:

On Friday, February 7, 2014 7:31:56 PM UTC+1, John Larkin wrote:
On Fri, 07 Feb 2014 10:04:23 -0800, Joerg <invalid@invalid.invalid


wrote:



John Larkin wrote:
On Wed, 05 Feb 2014 13:01:54 -0800, Joerg
invalid@invalid.invalid> wrote:
Folks, Need to sample stuff again. Essentially an equivalent
time deal like on older generation digital scopes where you
have a 20MHz or so ADC and GHZ-bandwidth on the scope. Can
take as long as it has to but ... the sampling must be
accurate and the sample gate should ideally close and open in
a few hundred picosends, 1nsec at the most. So far I've
always done this stuff in discretes, diode quads, brute-force
driver, the usual. But this gets old and now I need something
small and cheap. Aren't there any ICs in that domain or am I
the only one with such desires? Also looking for a timer chip
to run this but that's easier.
The classic sampling-scope circuit can be built cheap. SRD,
clip lines, 2-diode sampler, charge amp. This got about 5 GHz
bandwidth:
https://dl.dropboxusercontent.com/u/53724080/Protos/Sampler1.JPG

I was mulling a 2-diode sampler because then you don't get that
100% sampling pulse feed-through that you have with single-diode
sampling. But it doubles the capacitance. Doesn't it leak too
much?


Schottky diodes don't leak badly. You have to read it out in a few
us

after the sample.



There is also "blow-by", which is capacitive feedthrough of the

diodes. That is easily compensated with an opamp.



Sampling efficiency of a fast sampler (the output voltage over the

input voltage) is low, a few per cent maybe, but gain is cheap.



The classic HP 2-diode feedback sampler is well documented.


Is the 2 diode sampler used any more due to the delay of the
resistors in this configuration or is it another 2 diode sampler you
are referring to?

What would be good mathing diodes for the 4 diode samplers?

When I did my masters project we had to buy expensive quad packs,
probably hand-selected by a well paid HP employee. Came in a tiny
envelope. The ones they use for drugs nowaday

I don't think you can buy matched quads anymore and the closest to that
in performance would probably to buy a bridge quad in a single SMT
package, see page 1, bottom:

http://www.avagotech.com/docs/AV02-1388EN

They also make ring quads for RF mixers. But the purchasing department
has to keep a close eye on things because distributor stock can be
limited with these specialty devices.

Anything better would probably mean someone has to sit down and
hand-select diodes like the higher-end manufacturers did in the old days.

--
Regards, Joerg

http://www.analogconsultants.com/