Introduction : What is LED?


LED Lights
LED Lights

The full form of LED is Light Emitting Diode. An LED is an electronic semiconductor device that emits electromagnetic energy when supplied with a current.  The term LED is a general term that is mainly used in the field of lighting sources and technology.

LED is a semiconductor device with two terminals that is designed to produce light when an  electric current flows through it. It is made up of a junction of two semiconductors p-type and n-type semiconductors called as P-N Junction Diode.

Working of LED: Light Emitting Diode

The LED operates on the principle which states when the recombination of electrons and holes takes place, an energy is released in the form of light. The active region exits between the p and n regions. The light emerges from the active side in all the directions.

Symbol of LED
Symbol of LED

LED Construction
Construction of LED


LEDs are made of Gallium Arsenide (Ga As), Gallium Arsenide phosphide (Ga As P), Gallium Phosphide (Ga P). Silicon and  Germanium are not used because they are heat producing materials and are very poor in producing light.

Principle of LED Operation : How does LED works?

When the LED is forward biased, the electrons in the n-region will cross the junction and recombine with holes in the p-type material. These free electrons reside in the conduction band and when the recombination  takes place, they consequently generates the energy in the form of light.

Color of the Emitted Light :

The color of the emitted light decided by its wavelength and the semiconductor material used. The commonly available LED's emit green, blue, red, orange and yellow colors.

LED Color coding Characteristics
LED Color coding Characteristics

Characteristics of LED :

  • Operating temperature of LED ranges from -25°C to +60°C.
  • The forward voltage of an LED is between 1.8 and 3.3 volts. It varies by the color of the LED.
  • LED only works in forward bias mode.
  • LED emits light in all directions.
  • The power consumption of LED is typically 3 watts to 9 watts.

Advantages of LED :

  • LED's are small in size and light weight.
  • LED's have longer life as compared to the lamps.
  • LED's are available in different spectral colors.
  • LED's are suitable at high operating speeds as they take less than 1µs to turn on or off.
  • Power consumption in LED is very low, making them energy efficient.
  • Life Span of LED is much better than other lights.   

Applications of LED :

LED's are used in following applications

  • Opto-couplers
  • Infrared remote controls
  • Indicator lights
  • LED displays
  • TV & Mobile Back-lighting
  • Microprocessors
  • Traffic light control units

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