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[optoelectronics] how to protect a photodetector to avoid its saturation

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Doctorandus_P:
Maybe put a Zener (TVS) diode over the feedback resistor. This raises the photo diode current once the Zener starts conducting and therefore clamps the opamp output before it goes into saturation. But it shifts the problem to the speed of the Zener diode. TVS diodes are designed to be quick, but some do have a weird turn-off behavior after triggering.

Terry Bites:

Keep the sensor gain down. Keep the collector resistance low. Add gain later.

The Miller capacitance in the phototransistor can be an issue, try cascoding to neutralise it.

I agree, use a photodiode instead.
Many low cost PDs have rise and fall times in the 10nS area. eg an SFH203 has rise and fall times ~5nS
Use a servoed PD amplifier. It will reject the time integrated value of the illumnator IR.
That lets you apply high gain to fast events without getting blinded.

Aslo see https://tools.analog.com/en/photodiode/





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