Saturday, December 13, 2014

Light Emitting diode working principle; LED working principle


Lighting emitting diodes mostly known as LEDs are now becoming integrated part of every Industry, Household , Shops and everywhere as they offer plenty of advantages some of them main are such as power saving and long life.

There is curiosity arises how these LED’s will work?


Working principle of the same is as below:-

LED is capable of emitting a fairly narrow bandwidth of visible or invisible lights and LED emits lights usually of orange, red, yellow, or green colors. The invisible light that LED emits includes the infrared light.

LED consists of a P-N junction diode. When electric current is applied to that P-N junction then that junction emits light .This sensation is generally called Electro-luminance in electronics. Electro-Luminance is defined as the emission of light from a semi-conductor under the influence of an electric field.


At PN junction there are electrons at N- Region and Holes in P- region. These combine at PN Junction. Free electrons at N- Region are in the conduction band of energy levels, while holes in P-Region are in the valence energy band. When these high energy electrons combine with holes energy get emitted in the form of heat and light.

LED Symbol is shown below:-

LED, Light Emitting Diode



The electrons dissipate energy in the form of heat for silicon and germanium diodes.

There are some semiconductors such as :-
àGalium- Arsenide-phosphorous (GaAsP)

àGalium-phosphorous (GaP)
In above semiconductors electrons dissipate energy by emitting photons. If the semiconductor is translucent, the junction becomes the source of light as it is emitted, thus becoming a light emitting diode (LED).

Infrared light is produced by using Gallium Arsenide (GaAs) as semiconductor.
Red or yellow light is produced by using Gallium-Arsenide-Phosphorus (GaAsP) as semiconductor.

Red or green light is produced by using Gallium-Phosphorus (GaP) as semiconductor.


Characteristics for the same is as shown below:-

Light Emitting diode Characteristics

Very Small voltage is required to operate the LED's and there consumption is also very small.

For comparison between LED and Conventional lights Visit link below:-