Super fast sample & hold under $10?

[Joerg]

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.

--
Regards, Joerg

http://www.analogconsultants.com/

 

[Gerhard Hoffmann]

Am 05.02.2014 22:01, schrieb Joerg:

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?

You are not the only one, I was looking for sth. like that also.
You can get them if you buy a fast ADC on the same chip.

There is a fast T&H from Inphi, but not for $10.
I have found nothing else. :-(

regards, Gerhard

 

[Joerg]

Gerhard Hoffmann wrote:

Am 05.02.2014 22:01, schrieb Joerg:

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?

You are not the only one, I was looking for sth. like that also.
You can get them if you buy a fast ADC on the same chip.

There is a fast T&H from Inphi, but not for $10.
I have found nothing else. :-(

I did go through those but, as you hinted, anything in a reasonable
price range only has a T&H that goes to 250MHz. One went to around
800MHz but was almost 50 bucks. And you can't get the signal out in an
analog fashion but must use the ADC behind it. Plus sometimes those are
only 8-bits and that's a bit low in dynamic range.

So, looks like I have to roll my own. Again. ... <sigh>

I think I'll hop on my street bike now and pedal away the frustration.
Always seems to help and sometimes I get some fresh ideas.

--
Regards, Joerg

http://www.analogconsultants.com/

 

[Phil Hobbs]

On 2/5/2014 4:01 PM, Joerg 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.

Well, if you don't mind biasing it yourself, there's the HFA3102.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics

160 North State Road #203
Briarcliff Manor NY 10510

hobbs at electrooptical dot net
http://electrooptical.net

 

[Joerg]

Phil Hobbs wrote:

On 2/5/2014 4:01 PM, Joerg 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.


Well, if you don't mind biasing it yourself, there's the HFA3102.

Thanks. But that's just a transistor array, like using the old diode
quad. I guess I'll have to roll my own again.

This would be the real deal:

http://www.hittite.com/content/documents/data_sheet/hmc760lc4b.pdf

However ... 300 bucks :-(

For my masters project I could still obtain pouches of four matched RF
diodes each. That is becoming increasingly difficult and nowadays, while
you can get low capacitance bridge quads from Skyworks and others, they
are typically non-stock.

What always boggles my mind is this: The cost difference between making
your own beer versus buying a 12-pack of the good stuff is maybe 1:3.
Makes sense. For very fast S&H or T&H it is easily 1:50. Makes no sense.

--
Regards, Joerg

http://www.analogconsultants.com/

 

[Maynard A. Philbrook Jr.]

In article <lcuftk$npa$1@dont-email.me>,
pcdhSpamMeSenseless@electrooptical.net says...

On 2/5/2014 4:01 PM, Joerg 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.


Well, if you don't mind biasing it yourself, there's the HFA3102.

Cheers

Phil Hobbs

That's a nice chip. I can see a push pull with emitter limiter
transistor application there.

Or maybe a gilbert cell, any one up for a mixer ?

Jamie

 

[Joerg]

Maynard A. Philbrook Jr. wrote:

In article <lcuftk$npa$1@dont-email.me>,
pcdhSpamMeSenseless@electrooptical.net says...
On 2/5/2014 4:01 PM, Joerg 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.

Well, if you don't mind biasing it yourself, there's the HFA3102.

Cheers

Phil Hobbs

That's a nice chip. I can see a push pull with emitter limiter
transistor application there.

Or maybe a gilbert cell, any one up for a mixer ?

The capacitances are nice and low, very few hundred femtofarads.
Unfortunately it's a SO-14 package which introduces lots of inductance.
On fast switches that can really get you.

--
Regards, Joerg

http://www.analogconsultants.com/

 

[John Larkin]

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.

I'll put you down for two.


--

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

Precision electronic instrumentation

 

[Tom Miller]

"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

 

[John Larkin]

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
www.highlandtechnology.com jlarkin at highlandtechnology dot com

Precision electronic instrumentation

 

[Klaus Kragelund]

On Wednesday, February 5, 2014 10:01:54 PM UTC+1, Joerg 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.

I have never done fast S/H, so I'll excuse my suggestion forehand:

Wrap the sample and hold around a very fast comparator, like the:

http://www.analog.com/static/imported-files/data_sheets/ADCMP572_573.pdf

You probably need an open drain output type, let a cap ride on the output. Charge the cap, Then enable the comparator which in turn via a resistor discharges the cap and the comparator shuts of its own discharge. Start AD conversion.....

Cheers

Klaus

 

[Klaus Kragelund]

On Thursday, February 6, 2014 12:00:06 PM UTC+1, Klaus Kragelund wrote:

On Wednesday, February 5, 2014 10:01:54 PM UTC+1, Joerg 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.



I have never done fast S/H, so I'll excuse my suggestion forehand:



Wrap the sample and hold around a very fast comparator, like the:



http://www.analog.com/static/imported-files/data_sheets/ADCMP572_573.pdf



You probably need an open drain output type, let a cap ride on the output. Charge the cap, Then enable the comparator which in turn via a resistor discharges the cap and the comparator shuts of its own discharge. Start AD conversion.....

Of course, the precision is perhaps not up to your requirements, since it has 150ps prop delay...

What is the requirement for accuracy?

Cheers

Klaus

 

What always boggles my mind is this: The cost difference between making

your own beer versus buying a 12-pack of the good stuff is maybe 1:3.

Makes sense. For very fast S&H or T&H it is easily 1:50. Makes no sense.



--

Regards, Joerg



http://www.analogconsultants.com/

with the beer, you'll keep on drinking...

 

[Klaus Kragelund]

Wrt the switch, the idea was to use an open drain type, so it pulls low but when the output reaches the threshold, it switches so the cap is isolated with the body diode.

The input of the SH does not "see" the cap that way at all

Cheers

Klaus

 

[Joerg]

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?

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.

--
Regards, Joerg

http://www.analogconsultants.com/

 

[Joerg]

Klaus Kragelund wrote:

On Thursday, February 6, 2014 12:00:06 PM UTC+1, Klaus Kragelund
wrote:
On Wednesday, February 5, 2014 10:01:54 PM UTC+1, Joerg 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.
I have never done fast S/H, so I'll excuse my suggestion forehand:



Wrap the sample and hold around a very fast comparator, like the:



http://www.analog.com/static/imported-files/data_sheets/ADCMP572_573.pdf




You probably need an open drain output type, let a cap ride on the
output. Charge the cap, Then enable the comparator which in turn
via a resistor discharges the cap and the comparator shuts of its
own discharge. Start AD conversion.....

The problem is the switch, making the pulse is not a problem. The
comparator doesn't have any switch but you must disconnect the cap from
the signal source. Even Skyworks diodes are still 0.5pF (and unobtanium
....) which presents a ton of leakage at a GHz. Making a T or double-T
switch out of something like that gets really big and unwieldy.

Of course, the precision is perhaps not up to your requirements,
since it has 150ps prop delay...

What is the requirement for accuracy?

The prop delay does not matter. I need 100psec or so accuracy in pulse
position but the delay is not a concern.

--
Regards, Joerg

http://www.analogconsultants.com/

 

[Klaus Kragelund]

On Thursday, February 6, 2014 7:42:28 PM UTC+1, Joerg wrote:

Klaus Kragelund wrote:

Wrt the switch, the idea was to use an open drain type, so it pulls

low but when the output reaches the threshold, it switches so the cap

is isolated with the body diode.



The input of the SH does not "see" the cap that way at all





Maybe I misunderstand this, but there is no threshold. The signal is not

known and must be sampled to find out what the amplitude is at each time

slot. That can change significantly within a few hundred psec.

Implementation with sloooooooow comparator and emulation of reset of capacitor (open/closed switches):

https://dl.dropboxusercontent.com/u/44228185/FastSH.pdf

For actual application you would need a comparator with enable input and rescale values

Cheers

Klaus

 

[John Larkin]

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.

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.


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.

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


--

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

Precision electronic instrumentation

 

[Phil Hobbs]

On 02/06/2014 11:01 AM, Joerg wrote:

Klaus Kragelund wrote:
On Thursday, February 6, 2014 12:00:06 PM UTC+1, Klaus Kragelund
wrote:
On Wednesday, February 5, 2014 10:01:54 PM UTC+1, Joerg 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.
I have never done fast S/H, so I'll excuse my suggestion forehand:



Wrap the sample and hold around a very fast comparator, like the:



http://www.analog.com/static/imported-files/data_sheets/ADCMP572_573.pdf




You probably need an open drain output type, let a cap ride on the
output. Charge the cap, Then enable the comparator which in turn
via a resistor discharges the cap and the comparator shuts of its
own discharge. Start AD conversion.....



The problem is the switch, making the pulse is not a problem. The
comparator doesn't have any switch but you must disconnect the cap from
the signal source. Even Skyworks diodes are still 0.5pF (and unobtanium
....) which presents a ton of leakage at a GHz. Making a T or double-T
switch out of something like that gets really big and unwieldy.


Of course, the precision is perhaps not up to your requirements,
since it has 150ps prop delay...

What is the requirement for accuracy?


The prop delay does not matter. I need 100psec or so accuracy in pulse
position but the delay is not a concern.

Sounds like a job for a couple of pHEMTs in cascode. The SKY65050 is a
very nice device if its high 1/f corner (~50 MHz) doesn't worry you too
much.

Cheers

Phil Hobbs
--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics

160 North State Road #203
Briarcliff Manor NY 10510

hobbs at electrooptical dot net
http://electrooptical.net

 

[John Larkin]

On Thu, 06 Feb 2014 08:01:30 -0800, Joerg <invalid@invalid.invalid> wrote:

Klaus Kragelund wrote:
On Thursday, February 6, 2014 12:00:06 PM UTC+1, Klaus Kragelund
wrote:
On Wednesday, February 5, 2014 10:01:54 PM UTC+1, Joerg 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.
I have never done fast S/H, so I'll excuse my suggestion forehand:



Wrap the sample and hold around a very fast comparator, like the:



http://www.analog.com/static/imported-files/data_sheets/ADCMP572_573.pdf




You probably need an open drain output type, let a cap ride on the
output. Charge the cap, Then enable the comparator which in turn
via a resistor discharges the cap and the comparator shuts of its
own discharge. Start AD conversion.....



The problem is the switch, making the pulse is not a problem. The
comparator doesn't have any switch but you must disconnect the cap from
the signal source. Even Skyworks diodes are still 0.5pF (and unobtanium
...) which presents a ton of leakage at a GHz. Making a T or double-T
switch out of something like that gets really big and unwieldy.

We use SMS7621 diodes, around 0.25 pF. I can send you some.

Of course, the precision is perhaps not up to your requirements,
since it has 150ps prop delay...

What is the requirement for accuracy?


The prop delay does not matter. I need 100psec or so accuracy in pulse
position but the delay is not a concern.

A PHEMT might make an interesting series switch. They behave like jfets on
steroids. An NE8509 has about 0.35 pF drain capacitance and is about 6 ohms Rds
at zero gate bias. The capacitance could be "neutralized" with a balun
transformer inverter and another cap, or some dual-phemt balanced thingie.


--

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

Precision electronic instrumentation