FAQ - Roll your own preamp (Richard Hester design)

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Richard Hull
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Re: FAQ - Roll your own preamp (Richard Hester design)

Post by Richard Hull » Mon Oct 19, 2020 9:31 pm

Have you posted you circuit diagram? I saw the PCB image. I have a recommendation of the 2N4351A FET front end. (TO-72 case 4 lead) It has a +/-125 volt survival gate to source which is a plus.
The 2N4416 might be nice as well.

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
Retired now...Doing only what I want and not what I should...every day is a saturday.

Joe Gayo
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Re: FAQ - Roll your own preamp (Richard Hester design)

Post by Joe Gayo » Mon Oct 19, 2020 9:35 pm

I updated my post in the Richard Hester thread.
Last edited by Joe Gayo on Tue Oct 20, 2020 12:43 am, edited 1 time in total.

John Futter
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Re: FAQ - Roll your own preamp (Richard Hester design)

Post by John Futter » Tue Oct 20, 2020 12:34 am

I'll put up my design
It is a bit more than a preamp as it has post gain / shaping and a discriminator or lower window output to remove low energy pulses or noise for counting modes.
The analize output is suitable for direct connection to a MCA
It uses a cascode at the input to mitigate gate capacitance and raise the input impedance to way above any loading concerns
Shaping is controlled through C12 /R18
C11 should be near the same as input capacitance for best noise performance.
Preamp is senstitive to around 30 electrons of charge
The Test input / output is dual use you can inject a pulser signal here to check shaping / gain etc or a pot to set the discrimator clip level
for battery operation 2 PP9's and a 5 volt regulator (the second PP( for the neg bias for the cascode).
The bias terminal was originally used with minus 400 volts for a CZT detector up rating the capacitor voltage will allow whatever bias on whatever detector.
If using the preamp with a PMT couple to the amp input J1 (CON1) with a 2 pf capacitor

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Richard Hull
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Re: FAQ - Roll your own preamp (Richard Hester design)

Post by Richard Hull » Tue Oct 20, 2020 6:26 am

The FAQ will benefit all who read it in future with some electronic skills. I will cease working on Richard's design and wait for Joes boards to get here.

The boards I refer to are offered in the thread....

viewtopic.php?f=13&t=6092&start=60

Richard Hull
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
Retired now...Doing only what I want and not what I should...every day is a saturday.

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