Measuring Pulsing Current Output Average From Photodiode

[SHalas1]

Hello all,

I will be using a photodiode to measure optical power. The photodiode will convert this power into a current. The optical power will pulse rapidly in 15 ns periods with a 5 ns on-time (at full amplitude) and a 1 ns rise and fall time. I am looking for an analog averaging solution, i.e. an op-amp circuit that would give voltage outputs, say, every 1 us that are equivalent to the average voltage over the past 1 us. Ultimately, I need to be able to read the average voltage (proportional to an optical power, of course) every 5 us, but I am interested in oversampling at a rate of 5X in order to ensure I am not missing pulses in my pulse train and getting inaccurate readings. I have looked into "fast integrator op-amp" circuits, but I am still unsure if that will do the trick. Any suggestions would be greatly appreciated.

Thank you!

 

[berkeman]

Hello all,

I will be using a photodiode to measure optical power. The photodiode will convert this power into a current. The optical power will pulse rapidly in 15 ns periods with a 5 ns on-time (at full amplitude) and a 1 ns rise and fall time. I am looking for an analog averaging solution, i.e. an op-amp circuit that would give voltage outputs, say, every 1 us that are equivalent to the average voltage over the past 1 us. Ultimately, I need to be able to read the average voltage (proportional to an optical power, of course) every 5 us, but I am interested in oversampling at a rate of 5X in order to ensure I am not missing pulses in my pulse train and getting inaccurate readings. I have looked into "fast integrator op-amp" circuits, but I am still unsure if that will do the trick. Any suggestions would be greatly appreciated.

Thank you!

Welcome to the PF.

Sounds like a fun project. Is your photodiode at the end of a fiber? How is it picking up these light pulses?

The pulse width that you describe is fairly short, so you will need a specialized photodiode detector, IMO. What do you have in mind so far? And the first stage or two of the detector will not be jellybean opamps -- they should be fairly high speed detector amps, it would seem.