Fast amp for driving multiple T/Hs

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Along with another guy, I'm working on an idea that requires driving  
many T/Hs from a single signal.  The tradeoffs aren't clear yet, but  
it'll be something like M amplifiers driving N T/Hs each.  Ideally the  
sampled signal would have a small-signal bandwidth of about 600 MHz, and  
the resulting samples wouldn't need too much digital massaging  
afterwards to get a comprehensible result.

The sampling switches for the POC will be pHEMTs, either Mini-Circuits  
SAV-551+ or Renesas/CEL CE3512K2-C1.

(Sorry to be so mysterious, but my colleague's IP position requires it.)

So the question is: what's the best way to drive an ugly load consisting  
of N switches and N hold capacitors that are being switched successively  
during large-signal transients?

I've been working on a proto using EL5167ICZ buffers driving three pHEMT  
T/Hs with 22pF hold capacitors, but even with an amp that hot, it isn't  
yet apparent how to get the best waveform fidelity.

What are your fave fast amps for driving weird loads/

Thanks

Phil Hobbs

--  
Dr Philip C D Hobbs
Principal Consultant
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Re: Fast amp for driving multiple T/Hs
On Mon, 31 Aug 2020 19:23:33 -0400, Phil Hobbs

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Yikes, that sounds nasty. Assuming that the drains are the outputs to
the hold caps, there will be a bunch of charge injection to the left,
from the sources into the buffer amps. They tend to react somewhere
between mild disapproval and going totally nuts.

Gate drive will be interesting too, especially with the e-phempt
parts.

I like BUF602 for driving tough stuff fast.

Some longish xx-ohm traces might allow you to get the s/h thing over
with before the amp notices. You might even drive all the gates at the
same time and stagger the samples with txline lengths. Somebody made a
sampling scope like that once, namely a string of samplers spaced
along a transmission line.

I did the reverse once, injecting various height pulses simultaneously
into taps on a transmission line, to make a fast DAC. It modulates the
192 beam lines at NIF.



Re: Fast amp for driving multiple T/Hs
On 1/9/20 10:43 am, John Larkin wrote:
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That was Tom McEwan at LLNL. A semi-circular transmission line with  
sampling gates spread along it, and radial spokes to the sampling  
pulser, I believe.

CH.

Re: Fast amp for driving multiple T/Hs
wrote:

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This is one version of the distributed DAC.

https://www.dropbox.com/s/rym97ts13dt4qp5/T420_Amoeba.jpg?raw=1




--  

John Larkin         Highland Technology, Inc

Science teaches us to doubt.

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Re: Fast amp for driving multiple T/Hs
On 1/9/20 12:45 pm, snipped-for-privacy@highlandsniptechnology.com wrote:
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Do you calibrate-out the effect of each sampler removing some energy  
from the incoming signal?

I think McEwan's version had more stages - I saw 256 mentioned once.  
That must have been interesting in terms of power division.

CH


Re: Fast amp for driving multiple T/Hs
wrote:

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That's a DAC, not an ADC. I'm squirting signals into the line.



--  

John Larkin         Highland Technology, Inc

Science teaches us to doubt.

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Re: Fast amp for driving multiple T/Hs
On Mon, 31 Aug 2020 21:35:06 -0700, snipped-for-privacy@highlandsniptechnology.com
wrote:

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You can make a fast ARB from txline chunks and switches:

https://www.dropbox.com/s/io2by39xbvxdc63/TXline_Arb.jpg?raw=1



Re: Fast amp for driving multiple T/Hs

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Unfortunately, most of Tom McEwan's ideas were stolen from Larry  
Fullerton. Here's some notes I took of a government inquiry into McEwan's  
patents and the resulting cancellation of all his claims due to prior art  
by Fullerton.  

McEwan was also very active in stealing Fullerton's work in other areas.

Here are the notes, in no particular order.

The Development & Commercialization of Micropower Impulse Radar at

<BR>

Lawrence Livermore National Laboratory</B>

<P><B>A Report by the</B>

<P><B>Democratic Staff

<BR>

Committee on Science

<BR>

U.S. House of Representatives</B>

<P><B>April 9, 1999</B>


<P><I>The original is available at:
<A HREF="http://www.house.gov/science_democrats/archive/mirrpt99.htm ">  
http://www.house.gov/science_democrats/archive/mirrpt99.htm </A>.</I>

<LI>LLNL/UC and the MIR inventor, Thomas McEwan, were aware of  
Fullerton's inventions, but did not cite the inventions or other  
publications describing them to the Patent Office as is required by law;

<LI>TDC inventor Larry Fullerton invented and patented the same  
technology 7 years prior to LLNL/UC;

<P>In the late 1980s, claims were made regarding the ability of UWB radar  
to detect and identify stealth aircraft. The utilization of such a wide  
portion of the frequency spectrum to transmit information would  
reportedly enable the detection of stealth aircraft skins which absorb  
conventional radar, and the use of impulses to transmit information would  
reportedly allow the delineation of the sharp edges of stealth aircraft  
to a much higher degree than continuous-wave radar could. These claims  
were describedin several press articles in Aviation Week & Space  
Technology
<A HREF="#N12"> [12]</A> in 1989 and 1990.

<P>Two presentations
<A HREF="#N14"> [14]</A> on UWB radar were given by collaborators of  
Larry Fullerton at the March, 1990 LANL meeting. One presentation listed  
Mr. Fullerton as a co-author, and the other referred to his proprietary  
UWB radar equipment in the text of the paper.

<P>Also in attendance at that meeting were Thomas E. McEwan of LLNL and 9  
other LLNL employees. All known press reports
<A HREF="#N15"> [15]</A> of the meeting highlighted Fullerton's work,  
mentioning that he had secured several patents on the technology and  
describing his inventions.

<P>Records show that Thomas McEwan and other LLNL employees began  
targeted UWB radar R&D immediately upon their return from the March, 1990  
LANL meeting. Internal LLNL memos obtained by Democratic Staff indicate  
that Thomas McEwan had read at least one of the press reports surrounding  
the meeting which contained a description of Fullerton's inventions. In  
September, 1990, Thomas McEwan and David Christie (at that time also of  
LLNL) submitted an internal funding proposal entitled <U>Ultra-wideband  
TimeDomain Imaging Radar</U>. According to Mr. Christie's recollections,  
the proposal was funded. By February, 1991, LLNL was making UWB radar  
proposals to prospective industrial and governmental licensees,  
advertising a cheap, sensitive, low power, ultra-wideband radar that  
could fit on a single microchip.

<P>The first LLNL Invention Disclosure forms for MIR were filed in  
August, 1992. In 1993, LLNL/UC filed their first UWB radar patents on  
what would become known as MIR technology, listing Thomas E. McEwan as  
the inventor and UC as the patent owner. LLNL/UC did not cite any of  
Larry Fullerton's patents, publications, or articles describing TDC's  
inventions as prior art on their early MIR patent applications. MIR was  
characterized as a cheap, sensitive, low power, ultra-wideband radar  
technology that couldfit on a single microchip and that was ready to be  
licensed for use in a wide variety of applications including heartbeat  
monitors, power tools, and automotive collision sensors. Like Fullerton's  
radar inventions, MIR detects and identifies targets by relying on the  
reception and interpretation of very short, randomly-spaced impulses of  
electromagnetic energy that are reflected off the targets.

<A NAME="R16"></A>

<P>In September, 1995, after learning about the LLNL/UC patents, TDC  
contacted both LLNL and DOE and conveyed their beliefs that the  
inventions described in the MIR patents were extremely similar to  
Fullerton's inventions. This led to extensive correspondence between TDC  
(and its affiliated entity Pulson), LLNL/UC and DOE. LLNL/UC denied all  
of TDC's allegations, and maintained that the inventions were patentably  
different, and moreover, that LLNL/UC did not even begin targeted UWB  
radar work until 1992, 2years after the March, 1990 LANL meeting. On  
June 19, 1997, at the request of Dr. C. Bruce Tarter, Director of LLNL,  
TDC submitted extensive documentation to LLNL that summarized the dispute  
and suggested a potential settlement.
<A HREF="#N16"> [16]</A> This settlement was not accepted by LLNL/UC, no  
counter offer was made, and TDC's invitation to resolve the dispute using  
alternate dispute resolution was also turned down.

<A NAME="RepA2"></A>

<P><B>2. The Patent Reexamination</B>

  <BLOCKQUOTE>

<P><B>In May, 1998, the U.S. Patent and Trademark Office (PTO) rejected  
the 4core claims on LLNL's MIR motion sensor patent, as well as 8 of the  
remaining16 claims on the basis of the Fullerton patents.</B>


Here are the notes. The url is 404.

The Development & Commercialization of Micropower Impulse Radar at

<BR>

Lawrence Livermore National Laboratory</B>

<P><B>A Report by the</B>

<P><B>Democratic Staff

<BR>

Committee on Science

<BR>

U.S. House of Representatives</B>

<P><B>April 9, 1999</B>


<P><I>The original is available at:
<A HREF="http://www.house.gov/science_democrats/archive/mirrpt99.htm ">  
http://www.house.gov/science_democrats/archive/mirrpt99.htm </A>.</I>

<LI>LLNL/UC and the MIR inventor, Thomas McEwan, were aware of  
Fullerton's inventions, but did not cite the inventions or other  
publications describing them to the Patent Office as is required by law;

<LI>TDC inventor Larry Fullerton invented and patented the same  
technology 7 years prior to LLNL/UC;

<P>In the late 1980s, claims were made regarding the ability of UWB radar  
to detect and identify stealth aircraft. The utilization of such a wide  
portion of the frequency spectrum to transmit information would  
reportedly enable the detection of stealth aircraft skins which absorb  
conventional radar, and the use of impulses to transmit information would  
reportedly allow the delineation of the sharp edges of stealth aircraft  
to a much higher degree than continuous-wave radar could. These claims  
were describedin several press articles in Aviation Week & Space  
Technology
<A HREF="#N12"> [12]</A> in 1989 and 1990.

<P>Two presentations
<A HREF="#N14"> [14]</A> on UWB radar were given by collaborators of  
Larry Fullerton at the March, 1990 LANL meeting. One presentation listed  
Mr. Fullerton as a co-author, and the other referred to his proprietary  
UWB radar equipment in the text of the paper.

<P>Also in attendance at that meeting were Thomas E. McEwan of LLNL and 9  
other LLNL employees. All known press reports
<A HREF="#N15"> [15]</A> of the meeting highlighted Fullerton's work,  
mentioning that he had secured several patents on the technology and  
describing his inventions.

<P>Records show that Thomas McEwan and other LLNL employees began  
targeted UWB radar R&D immediately upon their return from the March, 1990  
LANL meeting. Internal LLNL memos obtained by Democratic Staff indicate  
that Thomas McEwan had read at least one of the press reports surrounding  
the meeting which contained a description of Fullerton's inventions. In  
September, 1990, Thomas McEwan and David Christie (at that time also of  
LLNL) submitted an internal funding proposal entitled <U>Ultra-wideband  
TimeDomain Imaging Radar</U>. According to Mr. Christie's recollections,  
the proposal was funded. By February, 1991, LLNL was making UWB radar  
proposals to prospective industrial and governmental licensees,  
advertising a cheap, sensitive, low power, ultra-wideband radar that  
could fit on a single microchip.

<P>The first LLNL Invention Disclosure forms for MIR were filed in  
August, 1992. In 1993, LLNL/UC filed their first UWB radar patents on  
what would become known as MIR technology, listing Thomas E. McEwan as  
the inventor and UC as the patent owner. LLNL/UC did not cite any of  
Larry Fullerton's patents, publications, or articles describing TDC's  
inventions as prior art on their early MIR patent applications. MIR was  
characterized as a cheap, sensitive, low power, ultra-wideband radar  
technology that couldfit on a single microchip and that was ready to be  
licensed for use in a wide variety of applications including heartbeat  
monitors, power tools, and automotive collision sensors. Like Fullerton's  
radar inventions, MIR detects and identifies targets by relying on the  
reception and interpretation of very short, randomly-spaced impulses of  
electromagnetic energy that are reflected off the targets.

<A NAME="R16"></A>

<P>In September, 1995, after learning about the LLNL/UC patents, TDC  
contacted both LLNL and DOE and conveyed their beliefs that the  
inventions described in the MIR patents were extremely similar to  
Fullerton's inventions. This led to extensive correspondence between TDC  
(and its affiliated entity Pulson), LLNL/UC and DOE. LLNL/UC denied all  
of TDC's allegations, and maintained that the inventions were patentably  
different, and moreover, that LLNL/UC did not even begin targeted UWB  
radar work until 1992, 2years after the March, 1990 LANL meeting. On  
June 19, 1997, at the request of Dr. C. Bruce Tarter, Director of LLNL,  
TDC submitted extensive documentation to LLNL that summarized the dispute  
and suggested a potential settlement.

<A HREF="#N16"> [16]</A> This settlement was not accepted by LLNL/UC, no  
counter offer was made, and TDC's invitation to resolve the dispute using  
alternate dispute resolution was also turned down.

<A NAME="RepA2"></A>

<P><B>2. The Patent Reexamination</B>

  <BLOCKQUOTE>

<P><B>In May, 1998, the U.S. Patent and Trademark Office (PTO) rejected  
the 4core claims on LLNL's MIR motion sensor patent, as well as 8 of the  
remaining16 claims on the basis of the Fullerton patents.</B>
  


Re: Fast amp for driving multiple T/Hs
On 1/9/20 2:11 pm, Steve Wilson wrote:
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Interesting. I knew that there was a patent dispute resolved in favour  
of TDS/Fullerton, but had assumed that it was a case of parallel  
development. McEwan did some really interesting things (e.g. switching  
1000V MOSFETs in 2ns, this parallel-sampling oscilloscope), but that's  
real scumbag behaviour.

Damn shame that TDS didn't bother to turn their inventions into useful  
products during the lifetime of their patents. The best way to defend  
your IP is to make a commercial success of it. Take the lead and run  
with it.

CH

Re: Fast amp for driving multiple T/Hs

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On Monday, September 25, 2000, Win Hill send me a pdf file and asked that  
I post it on my web site. His purpose was to discredit my analysis of the  
McEwan High-Speed Mosfet patent, 5,332,938.

Unfortunately, Win's analysis was faulty and did not show what he  
intended. In the circuit that was given, there was no way to propagate a  
2ns pulse into the mosfet. I sent my analysis to Win, but received no  
reply.

It would be interesting to post these files to the web, but unfortunately  
I suffered a devastating disk crash and lost all my google drive files as  
well as the logon info.

It should be noted that if you are religiously backing up your files to  
the same disk, your backups are worthless. You need to back up to a  
separate disk so if the first one gets wiped out like mine was, you still  
have working copies of your files.  


Re: Fast amp for driving multiple T/Hs
Steve Wilson wrote:
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   NOTED!!!!!!!!!!
   I got hosed the same way.

   $$$pending a lot of money for disk recovery only gets one tens of  
thousands of File001.*, File002.*, etc with each of dozens of file types  
having many thousands of files.

   Lots of duplicates really help increase the tediousness...
   And you see files that you forgot about years ago...and NOT see  
others that you damn know existed.

   One can spend months going thru that mess and only scratch he surface.

   Even the Mission Impossible team would quit due to poor real recovery  
results.

Re: Fast amp for driving multiple T/Hs

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I'm on VirtualBox. All I need are the vdi files, which contain the entire  
operating operating system and related files. The file recovery software  
cannot open vdi files, so it cannot harm them.

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I wrote my file manager. It indexes all the files on my disk and can go  
through 509,928 files in milliseconds. It makes finding any file easy.
  
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Re: Fast amp for driving multiple T/Hs
Steve Wilson wrote:
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* Of no help when tens of thousands of File001.*, File002.*, etc are  
already in (name) order.

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Re: Fast amp for driving multiple T/Hs
On 2020-09-01 00:11, Steve Wilson wrote:
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<snip>

There's a lot of bad blood between the weapons labs, especially  
Livermore and Los Alamos.  AIUI Teller (Livermore) got Oppenheimer (Los  
Alamos) canned in 1954, and the two parties have been at war ever since.

Cheers

Phil Hobbs

--  
Dr Philip C D Hobbs
Principal Consultant
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Re: Fast amp for driving multiple T/Hs

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You have to wonder how much that cost the nation.

Re: Fast amp for driving multiple T/Hs
John Larkin wrote:
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* 93-----------^^

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Re: Fast amp for driving multiple T/Hs
On 2020-08-31 20:43, John Larkin wrote:
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Yup.  With a depletion part, you just pur a resistor between gate and  
source--the ~HOLD pulse pulls the gate low via a good diode such as a  
BAT15.  Enhancement parts are more difficult, but in my current sitch  
it's basically just a few more RCs.

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Nice part--roughly an LH0063 with several times the bandwidth and better  
DC accuracy.  About the same slew rate though.

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Provided that the effects on the amp are repeatable, they can be  
calibrated out with no huge worries.
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Fun.  I've used various shorted-stub contraptions to make  
constant-fraction discriminator triggers for picosecond laser measurements.

Cheers

Phil Hobbs


--  
Dr Philip C D Hobbs
Principal Consultant
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Re: Fast amp for driving multiple T/Hs
On 2020-08-31 20:43, John Larkin wrote:
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Turns out the EL5167 + SAV-581 approach with a FIN1002 and 1PS10SB82
Schottky driving the gate works very well--the aperture time is well  
under 100 ps.  The FIN1002 has a fall time of 170 ps, and it only has to  
slew a volt or so to turn off the pHEMT.


Signal   |\ EL5167ICZ
0--------|-\
          |  >-*------*-----*    *----------------*--0  Sampled output
       *--|+/  |      |   S |    | D              |
       |  |/   |      R     --t-----             CCC
       |       |      R       |                  CCC
       *--RRRR-*      R 1k    |                   |
         402          |       |      30k         GND
                      *--|<|--*--*--RRRR-+5
                      1N4148     |
                                 |
                                 |
              /                  |
__r----    _/          FIN1002  |
                      |\         |
0-----RRRR---*-------|-\        |
       50     |       |  >--|<|--*
             CCC  Vt--|+/   1PS10SB82
        200p CCC      |/
              |
             GND

Turns out I needed to terminate the other end of the line with the  
ramp--otherwise it had noticeable steps.

I might not even need the diode and 1k resistor--I can just forward-bias  
the gate a bit because 50 uA or so isn't going to hurt it.

Cheers

Phil Hobbs

--  
Dr Philip C D Hobbs
Principal Consultant
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Re: Fast amp for driving multiple T/Hs
On Fri, 4 Sep 2020 10:20:55 -0400, Phil Hobbs

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I sometimes drive a SAV551 gate from cmos logic levels through just a
big-ish resistor. It forward biases nicely at a few uA of gate
current. You might use a resistor and a small bypass cap. If it always
turns off during the first half a volt of driver swing, sample time
will not depend on the signal level much.

Drive it from another SAV551!



This just got announced. It uses two SAV551s for switching three time
ranges. The "switch" is a trimpot with three positions and a complex
encoder circuit.

http://www.highlandtechnology.com/DSS/J270DS.shtml

R1 and R2 go to the gates.

https://www.dropbox.com/s/l1t3psx2d8xn06c/J270_Range_Switching.jpg?raw=1

Early in the lockdown, I was bored so designed this at home, PCB
layout too. I made it all analog so it didn't need any code.

This will run from a 24 or 48 volt wart. The first step is a little
sugar-cube switcher, a 7812 drop-in that tolerates up to 70 volts in.

Manufacturing is miffed at a couple of things that I did on the board
layout. Tough... I'm the boss.

The Amazon 10-watt attenuators seem to be pretty good, especially at
these speeds. I have some TDR/TDT pics I could post.



--  

John Larkin         Highland Technology, Inc

Science teaches us to doubt.

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Re: Fast amp for driving multiple T/Hs
On 2020-09-04 11:25, snipped-for-privacy@highlandsniptechnology.com wrote:
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I'll probably ditch the diode and replace the 1k with 2.7 pF to try to  
make sure that the gate enhancement doesn't tank at large positive slew  
rates.  Forward-biasing the gate will help a lot with that, I expect.

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That would save the diode capacitance and so might avoid the need for a  
bypass except at insane slew rates.  Still have circuit strays though.

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Fun.


Sure, that would be interesting.

Cheers

Phil Hobbs

--  
Dr Philip C D Hobbs
Principal Consultant
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