Introduction : A photo diode is a semi-conductor device, with a p-n junction and an intrinsic layer between p and n layers. It can be used as a light detector, which involves the conversion of light into current or voltage depending on mode of operation. [gallery ids="867,866" type="rectangular"] construction : Working : When a photon of sufficient energy strikes the diode, it creates an electron-hole pair. This mechanism is also known as the inner photoelectric effect. If it occurs at the junction these carriers are swept from the junction by the built-in electric field of the depletion region. Thus holes move toward the anode, and electrons toward the cathode, and a photo current is produced. The total current through the photo diode is the sum of the dark current (current that is generated in the absence of light) and the photo current, so the dark current must be minimized to maximize the sensitivity of the device. Mainly it is operated in two modes 1. Photo ...
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