Active matrix: Difference between revisions

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{{Short description|Addressing scheme in flat panel displays}}

'''Active matrix''' is a type of [[Display addressing scheme|addressing scheme]] used in [[flat panel display]]s. InIt thisis a method of switching individual elements (of a flat panel display, known as [[pixel]]s),. eachEach pixel is attached to a [[transistor]] and [[capacitor]] that ''actively'' maintainingmaintain 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 activeActive matrix technology was invented by [[Bernard J. Lechner]] at [[RCA]],<ref>{{Cite web |url=http://www.ieee.org/about/news/2011/honors_ceremony/releases_nishizawa.html |title=IEEE Jun-ichi Nishizawa Medal |website=[[Institute of Electrical and Electronics Engineers]] (IEEE) |access-date=2013-10-17 |archive-url=https://web.archive.org/web/20130912052239/http://www.ieee.org/about/news/2011/honors_ceremony/releases_nishizawa.html |archive-date=2013-09-12 |url-status=dead }}</ref> using [[MOSFET]]s (metal–oxide–semiconductor field-effect transistors).<ref>{{cite book |last1=Castellano |first1=Joseph A. |title=Liquid Gold: The Story of Liquid Crystal Displays and the Creation of an Industry |date=2005 |publisher=[[World Scientific]] |isbn=9789812389565 |pages=41–2 |url=https://books.google.com/books?id=vrtpDQAAQBAJ&pg=PA41}}</ref> Active matrix technology was first demonstrated as a feasible device using [[thin-film transistor]]s (TFTs) by [[T. Peter Brody]], Fang Chen Luo and histheir team at the Thin-Film Devices department atof [[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>{{Cite journal | doi = 10.1109/T-ED.1975.18214 | last1 = Brody | first1 = T. P. | last2 = Luo | first2 = 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| s2cid = 1378753 }}</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.

Another variant is to use diodes or resistors, but neither [[diode]]s (e.g. [[Metalmetal insulator metal diode]]sdiodes), nor non-linear voltage dependent [[resistor]]s (i.e. [[varistor]]s) are currently used with the latter not yet economical, compared to TFT.

The [[Macintosh Portable]] (1989) was perhaps the first consumer laptop to employ an active matrix panel.{{fact|date=August Today2022}} Since the decline of [[cathode-ray tube]]s, as a consumer display technology, virtually all TVs, computer monitors and smartphone screens that use [[LCD]] or [[OLED]] technology employ active matrix technology.<ref>{{cite web|title=What is OLED TV?|author=|date=1 March 2012|work=Cnet.com|url=http://reviews.cnet.com/8301-33199_7-57386898-221/what-is-oled-tv/}}</ref>

== See also ==

* [[AMLCD]]

* [[AMOLED]]

* [[QLED]]

* [[TFT-LCD]]

* [[Passive matrix addressing]]

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[[Category:Display technology]]

[[Category:Hungarian inventions]]