HW overview of the detector - RobertGawron/SemiconductorRadioactivityDetector GitHub Wiki

sensor circuit

Changes that I made during testing the device, that are not presented on the diagram:

U1 is OPA657U
U2 is OPA656U
R4 is 1G
As close as possible to input power socket are placed in paraller 1n/16V and 100n/16V, without them the device started to oscillate randomly.
A Schottky diode is connected in series after mentioned above extra capacitors to reduce risk of damaging the device when power supply is connected incorrectly. I don't know if it will help enough but I have already broke one PCB of this device this way, so now it's there.