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Photodiode under illumination

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Objective

Reverse-bias a BPW34 photodiode: the photocurrent is proportional to the irradiance.

Procedure

  1. Change the irradiance E (mW/cm²) in the Inspector: 1, 2, 5 and run.

Theory

In reverse bias the photodiode passes I = S·E (sensitivity × irradiance) plus a tiny dark current. With 10 kΩ in series the output voltage is I·R.

Questions to answer

  1. Why is photodiode current more linear than LDR resistance?

Components used

BPW34 photodiode, Battery / DC source, Resistor 220 ohm 1/4W

About the model

Ideal wires; component models as listed in the catalogue (no parasitics, no temperature drift). Built without a breadboard so the schematic stays readable.

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