Active matrix: Difference between revisions

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'''Active matrix''' is a type of [[addressing scheme]] used in [[flat panel display]]s. In this method of switching individual elements ([[pixel]]s), each pixel is attached to a [[transistor]] and [[capacitor]] ''actively'' maintaining the pixel state while other pixels are being addressed in contrast with the older [[passive matrix]] technology in which each pixel must maintain its state passively, without being driven by circuitry.

The active matrix technology was invented by [[Bernard J. Lechner]] at [[RCA]] and first demonstrated as a feasible device using [[thin-film transistor]]s (TFTs) by [[T. Peter Brody]] and his Thin-Film Devices department at [[Westinghouse Electric Corporation]] in 1974,<ref>[http://www.ieee.org/about/news/2011/honors_ceremony/releases_nishizawa.html IEEE Jun-ichi Nishizawa Medal]</ref> and the term was introduced into the literature in 1975.<ref name=OEDActiveMatrix>{{cite web|url=http://www.oed.com/viewdictionaryentry/Entry/1953#eid19485882 |title=Active Matrix|year=2011|work=[[OED]]|publisher=[[Oxford University Press]]}}{{subscription required}}</ref><ref name=Castellano>{{cite book|last=Castellano|first=Joseph A.|title=Liquid gold : the story of liquid crystal displays and the creation of an industry|year=2005|publisher=World Scientific|___location=New Jersey [u.a.]|isbn=978-981-238-956-5|pages=176|url=http://www.amazon.com/Liquid-Gold-Displays-Creation-Industry/dp/9812389563|edition=[Online-Ausg.]}}</ref><ref>{{citeCite journal doi| doi = 10.1109/T-ED.1975.18214 | last1 = Brody | first1 = T. P. | last2 = Fang Chen Luo | last3 = Szepesi | first3 = Z. P. | last4 = Davies | first4 = D. H. | title = A 6 x 6-in 20-lpi electroluminescent display panel | journal = IEEE Transactions on Electron Devices | volume = 22 | issue = 9 | pages = 739 | year = 1975}}</ref>

Given an ''m''&nbsp;&times;&nbsp;''n'' matrix, the number of connectors needed to address the display is ''m''&nbsp;+&nbsp;''n'' (just like in passive matrix technology). Each pixel is attached to a switch-device, which ''actively'' maintains the pixel state while other pixels are being addressed, also preventing [[crosstalk]] from inadvertently changing the state of an unaddressed pixel. The most common switching devices use TFTs, i.e. a [[field effect transistor|FET]] based on either the cheaper [[amorphous|non-crystalline]] [[thin-film]] [[silicon]] ([[amorphous silicon|a-Si]]), [[polycrystalline]] silicon ([[polycrystalline silicon|poly-Si]]), or [[Cadmium selenide|CdSe]] [[semiconductor]] material.