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 »

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
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
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Joe Gayo
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Re: FAQ - Roll your own preamp (Richard Hester design)

Post by Joe Gayo »

I updated my post in the Richard Hester thread.
Last edited by Joe Gayo on Mon Oct 19, 2020 8:43 pm, edited 1 time in total.
John Futter
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Re: FAQ - Roll your own preamp (Richard Hester design)

Post by John Futter »

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 »

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
The more complex the idea put forward by the poor amateur, the more likely it will never see embodiment
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