Light-emitting Diodes

A light-emitting diode (LED) is a specially manufactured diode that is designed in such a manner to glow, or emit light from it, when it is forward-biased. When it is reverse-biased, it will act just like any common diode; it will neither emit light nor it will allow considerable amount of current flow. LEDs can be designed to emit any color of the visible light spectrum we want, including “white” light. Red is found to be the most common color. For certain physical reasons, semiconductor material is especially efficient and sensitive to near-visible light in the infrared region. Consequently, many photoelectric eyes used for presence detection and industrial control functions operate in the infrared region.

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