Editing Active-matrix liquid-crystal display (section)

==Introduction==

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]].<ref>{{cite web|url=http://www.plasma.com/classroom/what_is_tft_lcd.htm |title=History of TFT LCD |quote=There are many kinds of AMLCD. For their integrated switching devices most use transistors made of deposited thin films, which are therefore called thin-film transistors (TFTs). |accessdate=2011-02-22 |url-status=dead |archiveurl=https://web.archive.org/web/20130823203913/http://www.plasma.com/classroom/what_is_tft_lcd.htm |archivedate=2013-08-23 }}</ref> 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 [[diode]]s. 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.