LED

WORKING, PRINCIPLE & VARIOUS APPLICATIONS OF LED

What Is An LED ?

  • LED stands for light emitting diode.
  • It is a semiconductor light source.
  • Mostly it is used for indication.
  • LED have two legs normally known as cathode & anode
  • Anode is a + ve terminal ( long leg )
  • cathode is a -ve terminal ( small leg )

WORKING OF LED

  • We can observe that the N-type silicon is in red color including the electrons which are indicated by the black circles.
  • The P-type silicon is in the blue color & it contains holes, they are indicated by the white circles
  • The power supply across the p-n junction makes the diode forward biased and pushing the electrons from n-type to p-type.pushing the holes in the opposite direction.
  • Electron and holes at the junction are combined.
  • The photons are given off as the electrons and holes are recombined.

APPLICATIONS OF LED

Old days

  • Signal indicators
  • umeric and alpha- numeric displays

Nowadays

  • automotive
  • Backlights
  • Flashlights for portable device
  • Signage
  • Torch lights
  • Projector light sources
  • Traffic lights
  • General illumination

BACKLIGHTS APPLICATIONS

  • Possible because of white LED development
  • Almost all mobile phone color LEDs use white LED backlighting
  • Size of displays from smallest to largest
  • Mobile phone,PDAs
  • Laptop PC monitors
  • LCD televisions

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