Connecting multiple PIN photodiodes to one amplifier

[ealex]

Hello

While preparing for another project i found some info about "Photodiode Gamma Ray Detector":
https://www.maximintegrated.com/en/app-notes/index.mvp/id/2236 or http://www.vk2zay.net/article/265

One photodiode is quite small -> chances of detecting something are small.
Looking at the maxim data note ( as i'll have to build something similar any way ) - can i connect multiple PIN diodes in parallel so i get a bigger detection area ?

[danadak]

Yes, but circuit behavior changes due to increased C. See the comments in
the ap note links you provided. You could consider using sampling approach
to problem looking at one diode at a time thru a mux. That would take careful
design as it intrinsically adds noise into the problem. Sampling on the order
of > 1 x N MSPS could be a starting point.

Or use a discrete buffer for each diode, maybe a SS JFET buffer might be
an approach.


Regards, Dana.

[ealex]

thanks Dana

i think i'll go for the first approach: connect several in parallel and update components value.
it will be just a quick and dirty experiment, as i already have the requested parts available

[Kleinstein]

A larger diode capacitance would reduce the resolution possible for the energy, as it would increase the noise. A better amplifier could help here a little.  So for best sensitivity in energy one would have separate amplifiers and peak detection for each diode. If the diodes are small it might be ok to parallel a few.

Having only separate amplifiers but still combine the signals to the ADC is only a partial solution.