After much searching I cannot find any ideas on how to protect our Perkin-Elmer APDs from overload conditions. I thought at one point I saw a schematic for a circuit that monitors the output current (a proxy for count rate) and flips a relay to power down the APD if a threshold is exceeded. I cannot find anything like that on the web. How does your group handle this issue?
In systems, it is done with custom circuit which current-limited voltage source (regulator). So you don't lock it off (although that is also possible) but just limit the average current preventing overheating .
In experiments, it is done be biasing the devices using Keithley 2400 (RS Stock No. 758-8853) while setting a suitable current limit.
Still, sometimes, an instant pulse from APD exposed to strong light may kill the preamp.
Nikolay Pavlov , thank you for the insight. It sounds like you bias your diodes directly, is that correct? We are using some SPCM-AQR sensors which are fed with a 5V supply.
Hi David, yes. It was something like these types of boards
https://www.ketek.net/store/products/pepcb-eval-mcx-res-p/
https://www.digikey.ie/product-detail/en/on-semiconductor/MICROFC-SMA-30050-GEVB/MICROFC-SMA-30050-GEVBOS-ND/9744737
In principle, at www.ndevices.ie I do custom developments of such kind.
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