Hey, This is a somewhat tangent to my photomultiplier thread but pretty distinct.
I have a bunch of preamplifier boards from PMT's, which are constructed as little DIN41612 plugin boards. No info beyond that.
They are really nice, though, with an exotic dual FET input stage and a nice AD744 op amp.
I'd like to reuse them for my scintillation/cherenkov counting adventures, however their function puzzles me somewhat.
I've traced the schematic from the pcb, and it looks like they have +-V, GND, out, and 2 input pins.
Now, from the feedback stuff and BAV45 "picoampere" diodes and feedback network, I believe pin 16 must be main input,
That just leaves pin 8 as an unknown input. Can anyone deduce what its function is? Is it just some programmable offset thing?
I'm not deep enough into these circuits to deduce whether this is optimized for pulse counting (single photon, what I'm looking for) or some continuous light level thing, what do you think?
The two unknown components looks like laser trimmed resistors, but unfortunately I don't have my good multimeter with me so I'm unsure of their values.
Maybe thermistors for temp. co?
Thanks for the interest!
--Chris