Active-matrix liquid-crystal display
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An active-matrix liquid-crystal display (AMLCD) is a type of flat-panel display used in high-resolution TVs, computer monitors, notebook computers, tablet computers and smartphones with an LCD screen, due to low weight, very good image quality, wide color gamut and fast response time.
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The concept of active-matrix LCDs was proposed by Bernard J. Lechner at the RCA Laboratories in 1968.[1] The first functional AMLCD with thin-film transistors was made by T. Peter Brody, Fang-Chen Luo and their team at Westinghouse Electric Corporation in 1972.[2][3] However, it took years of additional research and development by others to launch successful products.
The term "active matrix" was coined by T. Peter Brody in 1975.[4]
The most common type of AMLCD contains, besides the polarizing sheets and cells of liquid crystal, a matrix of thin-film transistors to make a thin-film-transistor liquid-crystal display.[5] These devices store the electrical state of each pixel on the display while all the other pixels are being updated. This method provides a much brighter, sharper display than a passive matrix of the same size. An important specification for these displays is their viewing-angle.
Thin-film transistors are usually used for constructing an active matrix so that the two terms are often interchanged, even though a thin-film transistor is just one component in an active matrix and some active-matrix designs have used other components such as diodes. Whereas a passive matrix display uses a simple conductive grid to apply a voltage to the liquid crystals in the target area, an active-matrix display uses a grid of transistors and capacitors with the ability to hold a charge for a limited period of time. Because of the switching action of transistors, only the desired pixel receives a charge, and the pixel acts as a capacitor to hold the charge until the next refresh cycle, improving image quality over a passive matrix. This is a special version of a sample-and-hold circuit.
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