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Ques : Describe a Liquid Crystal Display

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 LCDs are the screens of choice for portable computers and lightweight screens. They consume very little electricity and have advanced technologically to quite good resolutions and color support. They were developed by the company RCA in the 1960s. LCDs function simply by blocking available light so as to render display patterns.

LCDs can be of the following types:

  1. Reflective LCDs: Display is generated by selectively blocking reflected light.
  2. Backlit LCDs : Display is due to a light source behind LCD panel.
  3. Edgelit LCDs : Display is due to a light source adjacent to the LCD panel.


LCD Technology
The technology behind LCD is called Nematic Technology because the molecules of the liquid crystals used are nematic i.e. rod-shaped. This liquid is sandwiched between two thin plastic membranes. These crystals have the special property that they can change the polarity and the bend of the light and this can be controlled by grooves in the plastic and by applying electric current.

Passive Matrix
In a passive matrix arrangement, the LCD panel has a grid of horizontal and vertex conductors and each pixel is located at an intersection. When a current is received by the pixel, it becomes dark. This is the technology which is more commonly used,

Active Matrix
This is called TFT (Thin Film Transistor) technology. In this there is a transistor at every pixel acting as a relay, receiving a small amount and making it much higher to activate the pixel. Since the amount is smaller, it can travel faster and hence response times are much faster. However, TFTs are much more difficult to fabricate and are costlier

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