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I have a pretty quick question. I am working with a laser diode with an integrated photodiode. The pin configuration has a common cathode connection for bother the laser and photodiode. I want to power the laser diode but also operate the photodiode in photovoltaic mode as you get better response, however I am unsure if this is possible.

My example circuit is shown below, if I apply a voltage across the laser diode and then for sake of argument connect a resistor unto ground across the photodiode for a probe to measure the voltage induced from the photodiode current. Will the Current source, which is a lab supply with current limit, not provide an additional unaccounted for voltage across both the photodiode and resistor?

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?

schematic

simulate this circuit – Schematic created using CircuitLab

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  • \$\begingroup\$ The current source and model numbers of the LED and photodiode are purely as symbol representations, they are not the relevant numbers or codes respectively of my setup. \$\endgroup\$
    – Tricks
    Apr 11, 2016 at 15:52

1 Answer 1

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"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.

schematic

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.

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  • \$\begingroup\$ So is this Falstad circuit simulation show that the voltage applied to the laserdiode will not affect the photdiode? link \$\endgroup\$
    – Tricks
    Apr 12, 2016 at 10:22
  • \$\begingroup\$ I'm not sure what you mean. I1 loops through the diode, and that's all. How could it go through D2? \$\endgroup\$
    – WhatRoughBeast
    Apr 12, 2016 at 13:29

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