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what is led

What is LED- Working and Applications of Light Emitting Diode

This article is based on the Light Emitting Diode, working and operations of Light Emitting Diode (LED) and the applications of Light Emitting Diode (LED).

In our previous articles we learn about diodes and the working of diodes and the applications of a diode as half wave rectifier, clipper circuit, clamper circuits but this is not the end for the applications of a diode, A diode can do much more. A number of specific types of diodes are manufactured for specific applications. Some of the more common special-purpose diodes will be covered in this series.(i) Zener diode (ii) Light-emitting diode (LED) (iii) Photo-diode (iv) Tunnel diode (v) Varactor diode and (vi) Shockley diode.

What is the Light Emitting Diode (LED)?

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A Light Emitting Diode (LED) is the special purpose diode. It gives visible light when it is forward biased. Light Emitting Diodes (LEDs) are widely used for indication purpose.

Why Are LEDs Special Purpose of Diode?

Light Emitting Diode (LED) are the special type of diode because they are not made from Silicon or Germanium, Basically, they are made from elements like Gallium, Phosphorus, and Arsenic. By varying the quantity of these elements, it can produce a different type of colors.

  • It is possible to produce different colors by varying the wavelengths which result to form colors like red, green, blue, and yellow.

For example, Gallium arsenide based LED will produce a red light.  And if the LED is made with gallium phosphide, it will produce a green light.

Symbol of Light Emitting Diode (LED):

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symbol of LED

Terminals of LED:

working of light emitting diode (LED)


Biasing of Light Emitting Diode (LED):

Usually, Diode conducts voltage when it is greater than 0.7V for silicon and 0.3 for Germanium but in case of LEDs. As they are made up of different materials like gallium arsenide and gallium phosphide they conduct when the input voltage is greater than the 1.2V to 3.2V.

Working of Light Emitting Diode (LED):

When the LED is forward-biased:

  • When a light-emitting diode is forward bias then the electrons from the n-type material cross the PN junction and recombine with holes in the p-type material.
  • As free electrons (are in conduction band) and these are at a higher energy level than the holes (in the valence band).
  • When the recombination takes place, the electrons release energy in the form of heat and light (Photons).
  • In materials like gallium arsenide and gallium phosphide, the number of photons of light energy is sufficient to produce quite visible light.

forward bias of Light emitting diode

Advantages of LED

The light-emitting diode (LED) is a very useful light source. LEDs have replaced older lamps in many applications because they have the following advantages:

  1. Low voltage
  2. Longer life (more than 20 years)
  3. Fast response time (on-off switching)

Applications of LEDs:

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You can find LEDs all around our life. They are indoors they are in outdoors, they are used in the following areas and circuits:

They are widely used for indication purpose:

  1. In cars and other vehicles for indication purpose
  2. In data displaying LCDs.
  3. In Traffic lights for sign and signals.
  4. They are used in toys and medical equipment’s.
  5. They are used in decorations
  6. They are used in remote controls and much more.

They are widely used in Seven-segment display.

  1. LEDs are grouped to form 7 segment displays.
  2. 7 segment displays are widely used for counting objects.
  3. They are used for displaying numbers
  4. They are used in digital voltmeters and ammeters
  5. They are used in computers, laptops, and mobile phones.
  6. They are used in calculators.
  7. They are used in cloaks and Timer circuits.
  8. They are used in many areas (CNG PUMPS, HOSPITALS, BANKS, AIRPORTS, ETC).
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Biasing of PN Junction – Forward Bias & Reverse Bias



    This article reminds me on my physics lessons on LED. I like the way you’ve described the working and its applications. Very good article to a physics or industrial professional.

    • Sohailanwar

      Thanks, I will make sure to update my every article informative. Stay connected to learn best.

  2. manoj

    how does multicolor led’s work?????

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