This is mostly for John Larkin.
You should be able to find a PDF atthe above site.
I used only a 10Meg ohm resistor in the front end TIA circuit. There was a bit of extra noise from the current source, but certianly nothing near shot noise. There was no attempt on my part to make the current source low noise, I suspect the extra noise is from the Voltage reference from which the current source is derived. (10 Volt refernce through a 1 Gig ohm resistor)
I did notice that there was some vibrational pickup. If I banged on the box I'd get noise spikes and could see some oscillations at 300 to
500 Hz. These are leaded 1 Gig ohm resistors and it could be it was vibrating.George H.