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I'm designing a transimpedance amplifier for a SiPM (Silicon Photo Multiplier Array Broadcom AFBR-S4N44C013) sensor. I want the output voltage to range between 0 and 3.2 V max so I can input it into an Arduino.

I'm using a 36 V bias voltage from a custom 3.2 V to 36 V booster. The main issue I'm facing right now is that even though the output of the op-amp varies proportionally with the brightness, the range is in the millivolts (20 - 100 mV) when the power is on and 0 - 45 mV when the power is off. Changing the feedback resistor R5 to 100k fixed the opamp output at around 0 V. Any suggestions for how to fix this and amplify the output to the desired range?

I've attached the schematic. Also, the buffer section of the circuit is not being used right now. If you have any suggestions for how to fix the issue that the buffer is powered by 3.3V but receives the full 36V, that would help too.

Here's the datasheet of the SiPM: https://docs.broadcom.com/doc/AFBR-S4N44C013-DS

Thank you.

Schematic

truncatingtelescopes
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  • https://github.com/OpenSiPM/sipm-bias-control You might be interested in this SiPM transimpedance design. Note the low noise bias generator and the negative voltage rail (which you need). Also includes an Arduino. Maybe you can borrow some things. – user1850479 Jul 19 '23 at 01:12
  • Not an answer but I wish all of the engineers that work for me drew schematics like yours – Luke Gary Jul 19 '23 at 02:55

3 Answers3

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Your configuration of the photodiode and bias voltage will generate a positive current into the summing node of the TIA. This will generate a negative voltage out of the TIA. You have no negative supply for the TIA, so it will be pinned at GND.

For a positive output voltage from a TIA you will need a negative bias voltage for the PD (and reverse the PD polarity).

elchambro
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First off, you have no low pass filter cap on your TIA, so you'll get the full bandwidth of the noise, you need a cap to limit the bandwidth. Set the filter of the TIA to whatever the measuring device is.

In addition, there is also noise from the SiPM and the 36V line. If your AC noise of the 36V line is in the mV range then that is the likely source. The 36V line will need to be clean, use a linear tech LDO, a good one or a really low noise LDO to filter the 36V.

Voltage Spike
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The lack of a negative rail was already pointed out, but even if you fix that, there is a more fundamental issue: R5 is so small the transimpedance amplifier is pointless. It is only adding noise, so you can actually improve your sensitivity (slightly) by removing it.

Compare to a simple 250 ohm resistor, which like your amplifier also has a transimpedance gain of 250 ohms. While the gain would be equal, your bandwidth would be determined by the RC filter from the resistor (250 ohms) and SiPM capacitance (990pF). 3dB bandwidth would be 1/(2pi250*990E-12) = 640 KHz. Conversely your TIA is about ~800 KHz bandwidth once you fix the missing feedback capacitor. So you can get the same gain and nearly the same bandwidth but none of the amplifier noise by not populating U1!

You might still want a transimpedance amplifier if you decided you wanted a lot more gain. For example, if you went with 100k, then your RC bandwidth with a resistor would be only 1.6 KHz. If that wasn't fast enough, you should then look at a TIA, probably with a faster opamp though.

user1850479
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