light-sensoroperational-amplifierphotodiodetransimpedance
I want to use a photodiode to measure light intensity, but I am not sure if the photodiode should be used in photoconductive or photovoltaic mode.
From my understanding the photovoltaic configuration will have a leakage current proportional to light intensity and the photoconductive configuration will produce a current proportional to the light intensity. Both seem like the would work for my application.
Will either configuration work? and is there a benefit to using one over the other?
You are using exactly the same circuit you used in Ambient light rejection from photodetecting circuit, and I will repeat what I said in that question.
Reduce C6. You have gotten better results by reducing C6 from 1 uF to 0.01 uF. Reduce C6 to 1000 pf (.001 uF) and you will get even better results.
C6 and R1 are combining to form a low-pass filter. With 220k and 1 uF, response will drop to 1/2 of DC when the signal frequency f $$f = \frac{1}{2\pi RC}$$ For your original circuit, this was 1.3 Hz.
When you reduced C6 this became 130 Hz.
Note that these numbers apply to sine waves. It's more complicated with your nominal square waves.
As I said in my earlier answer, you can certainly reduce C6 to 1000 pf (.001 uF). You can very likely reduce it to 100 pF, and get even faster response. Much below 100 pF and, considering your physical layout, you may have stability problems.
"Is there a circuit setup that will allow me to operate the photodiode in photovoltaic mode without voltage/current being supplied to the laser diode affecting it?'
You bet.
simulate this circuit – Schematic created using CircuitLab
But, of course, you'll probably have noticed that this isn't much different from your original circuit.
Best Answer
Right, except for photovoltaic it's not leakage current... just photocurrent. The biased version will give a little more dark current. The big advantage of biasing the photodiode is that you reduce it's capacitance. (typical numbers might be by a factor of 4 or 5. at 10V) And this makes the detector faster. Which is almost always a good thing. Oh one final disadvantage to the bias case is that any noise on the bias voltage appears on the output. (so filter the bias supply.)