Light Emitting Diode

Light-emitting diodes, or LEDs, are widely used as a standard source of light in electrical equipment. It has a wide array of applications ranging from your mobile phone to large advertising billboards. They are extensively made for the use in devices for showing what the time is and for displaying different types of data. In this post, the main focus would be on learning a lot about LED such as its operations and functions.

What is LED?

A light releasing diode is an electric component that emits light when the electric current flows through it. It is a light source based on semiconductors. When current passes through the LED, the electrons recombine with holes emitting light in the process. It is a specialised type of diode having similar characteristics as the p-n junction diode. This, in turn, means that an LED allows the flow of current in its forward direction while it blocks the flow in the reverse direction. Light-emitting diodes are made from a very thin layer of heavily doped semiconductor material. Based on the semiconductor material used and the amount of doping, an LED will emit a coloured light at a particular spectral wavelength when forward biased.

Light Emitting Diode

 

LED Circuit Symbol

The figure demonstrates the LED symbol: this would be somewhat similar to the p-n junction diode where the only change would be that the two arrows would indicate that the diode would emit the light.

Symbol of LED
Given in the table below are the links related to LED:

Light Emitting Diode Circuit

The LEDs also have a specific drop in voltage forward in cases where it is used normal circuits like a conventional diode. The drop in voltage depends on the current of LED, the colour of the produced light, etc. There are different values in the drop of voltage that would vary from 1.5V to 2.5 V current for 10 to 50 mA current.

LED Circuit Diagram

Working Principle of LED

The holes lie in the valence band and the free electrons are placed in the conduction band. When there is a forward bias in the p-n junction, the electron which is a part of the n-type semiconductor material would overrun the p-n junction and join with the holes in the p-type semiconductor material. Therefore regarding the holes, the free electrons would be at the higher energy bands.

Working Of LED
The figure demonstrates the elementary process principle.
When there is a recombination of free electrons at the hole,  there would be a change regarding the energy level concerned from a value that is higher to the value that is lower and it drops from the conduction band to the valance band.  There is a release of energy due to the motion of the electron. In standard diodes, the release of energy in the manner of heat. But in LED the release of energy in the form of photons that would emit the light energy. The entire process is termed as electroluminescence and the diodes are termed as a light-emitting diode.

In LED, energy discharged in light form hinges on the forbidden energy gap. One could manipulate the wavelength of the light produced. Therefore, the light colour and its visibility or not could be controlled from its wavelength. The colour and wavelength of the light emitted can be determined by doping it with several impurities.

Uses of LED

LEDs are used in a wide variety of applications, including optical communication, alarm and security systems, remote-controlled operations, robotics etc. It finds usage in many such areas because of its long-lasting capability, low power requirements, swift response time and fast switching capabilities. Some common LED uses are given in the points below.

  • Used for tv backlighting
  • It is used for smartphone backlighting
  • Uses in displays
  • Used in automotive
  • LEDs used in the dimming of lights

Types of LED

There various types of LED or light-emitting diode which are made of semiconductors and are classified into different categories according to the properties of LED. Check the different types of LED given below.

  • Miniature LEDs
  • High-Power LEDs
  • Flash LED
  • Bi and Tri-Colour
  • Red Green Blue LEDs
  • Alphanumeric LED
  • Lighting LED

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