Infrared Emitting Diodes

IREDs or InfraRed Emitting Diodes are a type of LEDs which emit light in the infrared range of the electromagnetic spectrum. IREDs are widely used in process control, optical switching circuits and Logic circuits.

Like LEDs, Infrared Emitting Diodes are PN junctions which emit light when connected in a forward bias.  Under forward bias conditions, the carriers are given energy to cross the depletion layer.  On crossing the depletion layer, the carriers, both holes and electrons recombine.  Energy is released in the process of recombination in the form of a photon.

One common application where Infrared Emitting Diodes are used is the TV remote

Infrared Emitting Diodes are made of materials such as Gallium Arsenide (GaAs) and Gallium Aluminium Arsenide (GaAlAs). 

IREDs emit radiation at wavelengths such as 880nm and 940 nm (nanometres).  Thus, they are ideal for switching on phototransistors which are sensitive to electromagnetic radiation at such wavelengths.

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