Write in brief about Photo-diodes.

Explanation

Photo diode: A reverse biased special p-n junction diode having transparent window is known as photo diode. When photo diode is illumination with light, the reverse diode current varies linearly with the light flux. Working: This diode is always reverse biased but the voltage applied is less than the break down voltage. When light of suitable frequency is incident on the photodiode, more electrons move from valence band to conduction band (if teh energy of incident photon is more than the forbidden energy gap) and as a result current in the circuit increases. As the intensity of incident light is increased, current goes on increasing till it becomes maximum.