LIGHT EMITTING DIODE (LED), PRINCIPLE OF OPERATION ~ SCC Education

Thursday, 18 February 2016

LIGHT EMITTING DIODE (LED), PRINCIPLE OF OPERATION

LIGHT EMITTING DIODE (LED)

An LED is a specially fabricated P-N junction diode that emits monochromatic light when it is forward biased.

LED is invented 1^st by “OLEG LOSEV “in 1927.

First practical of visible spectrum (red) was developed in 1962 by “NICK HOLONYAK”. so He is called the FATHER of LED.

In 1968 “Man Santo company” was the first organization to mass produce visible LEDs using GaAsp .

The lifetime of LEDs are 25000 to 100000 hours. But heat and current setting can extend or shorten this time.

PRINCIPLE OF OPERATION

The operation of LED is based upon the phenomenon of electro luminance

When a P-n junction is f/w biased then free electrons cross the

N-region and recombine with holes existing in p-region .

free electrons are in C.b. (high energy level) while holes are in V.b. ( low energy level).

As these electrons fall from higher energy to lower energy level recombine with holes then these radiated energy in the form of heat and light

Led produces light while conducting current through them so led are current driven devices.

COLOR OF LED

The color of light emitting diode depends upon various factors such as

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