In this note, Poly Notes Hub will discuss about the Light Emitting Diode or LED. Welcome to our website, India’s best blogging site for Polytechnic Notes.
Author Name: Arun Paul.
What is Light Emitting Diode or LED ?
A light-emitting Diode is a diode that gives off visible light when forward-biased.
Construction
Light-emitting diodes are not made from silicon or germanium but are made by using elements like gallium, phosphorus, and arsenic. By varying the quantities of these elements, it is possible to produce light of different wavelengths with colors that include red, green, yellow, and blue. For example, when a Light-Emitting Diode is manufactured using gallium arsenide, it will produce a red light. If the Light-Emitting Diode is made with gallium phosphide, it will produce a green light.
Working
When light-emitting diodes are forward biased as shown in Fig (i), the electrons from the n-type material cross the PN Junction and recombine with holes in the p-type material. Recall that these free electrons are in the conduction band and at a higher energy level than the holes in the valence band. When recombination takes place, the recombining electrons release energy in the form of heat and light. In germanium and silicon diodes, almost the entire energy is given up in the form of heat and emitted light is insignificant. However, in materials like gallium, and arsenide, the number of photons of light energy is sufficient to produce quite intense visible light.
Fig (ii). shows the schematic symbol for a Light-Emitting Diode. The arrows are shown as pointing away from the diode, indicating that light is being emitted by the device when forward-biased. Although Light-Emitting Diodes are available in several colors (red, yellow, and orange are the most common), the schematic symbol is the same for all LEDs. There is nothing in the symbol to indicate the color of a particular LED.
Advantages
Below we listed some advantages of Light-Emitting Diode –
- Operating voltage is very low.
- Longer life ( More than 20 years )
- Fast ON-OFF switching
Applications
Below we listed some uses of Light-Emitting Diode –
- Used as an Indicator
- Used in Seven Segment.
- Light Bulbs and Many more.
