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CBSE Class 12 · 2010 · SemiconductorsShort Answer

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Draw the circuit diagram of an illuminated photodiode in reverse bias. How is a photodiode used to measure light intensity?

Solution

Connect the photodiode in reverse bias (p-side to −, n-side to +) with a transparent window exposing the junction.
Incident photons of energy create electron-hole pairs in the depletion region; these are swept across the junction giving a reverse photocurrent.
Since the number of pairs produced per second is proportional to the light intensity, the photocurrent is proportional to the intensity and can be used to measure it.

CBSE Class 12 Board · 2010 · Subjective

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