Active matrix is a type of addressing scheme used in flat panel displays. It is a method of switching individual elements of a flat panel display, known as

pixel In digital imaging, a pixel (abbreviated px), pel, or picture element is the smallest addressable element in a Raster graphics, raster image, or the smallest addressable element in a dot matrix display device. In most digital display devices, p ...

s. Each pixel is attached to a

transistor A transistor is a semiconductor device used to Electronic amplifier, amplify or electronic switch, switch electrical signals and electric power, power. It is one of the basic building blocks of modern electronics. It is composed of semicondu ...

and

capacitor In electrical engineering, a capacitor is a device that stores electrical energy by accumulating electric charges on two closely spaced surfaces that are insulated from each other. The capacitor was originally known as the condenser, a term st ...

that ''actively'' maintain 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. Active matrix technology was invented by Bernard J. Lechner at RCA, using

MOSFET upright=1.3, Two power MOSFETs in amperes">A in the ''on'' state, dissipating up to about 100 watt">W and controlling a load of over 2000 W. A matchstick is pictured for scale. In electronics, the metal–oxide–semiconductor field- ...

s (metal–oxide–semiconductor field-effect transistors). Active matrix technology was first demonstrated as a feasible device using

thin-film transistor A thin-film transistor (TFT) is a special type of field-effect transistor (FET) where the transistor is made by thin film deposition. TFTs are grown on a supporting (but non-conducting) substrate, such as glass. This differs from the convention ...

s (TFTs) by T. Peter Brody, Fang Chen Luo and their team at the Thin-Film Devices department of

Westinghouse Electric Corporation The Westinghouse Electric Corporation was an American manufacturing company founded in 1886 by George Westinghouse and headquartered in Pittsburgh, Pennsylvania. It was originally named "Westinghouse Electric & Manufacturing Company" and was ...

in 1974, and the term was introduced into the literature in 1975. Given an ''m'' × ''n'' matrix, the number of connectors needed to address the display is ''m'' + ''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 In electronics, crosstalk (XT) is a phenomenon by which a signal transmitted on one circuit or channel of a transmission system creates an undesired effect in another circuit or channel. Crosstalk is usually caused by undesired capacitive, ...

from inadvertently changing the state of an unaddressed pixel. The most common switching devices use TFTs, i.e. a FET based on either the cheaper non-crystalline thin-film

silicon Silicon is a chemical element; it has symbol Si and atomic number 14. It is a hard, brittle crystalline solid with a blue-grey metallic lustre, and is a tetravalent metalloid (sometimes considered a non-metal) and semiconductor. It is a membe ...

( a-Si),

polycrystalline A crystallite is a small or even microscopic crystal which forms, for example, during the cooling of many materials. Crystallites are also referred to as grains. Bacillite is a type of crystallite. It is rodlike with parallel longulites. S ...

silicon ( poly-Si), or CdSe

semiconductor A semiconductor is a material with electrical conductivity between that of a conductor and an insulator. Its conductivity can be modified by adding impurities (" doping") to its crystal structure. When two regions with different doping level ...

material. Another variant is to use diodes or resistors, but neither

diode A diode is a two-Terminal (electronics), terminal electronic component that conducts electric current primarily in One-way traffic, one direction (asymmetric electrical conductance, conductance). It has low (ideally zero) Electrical resistance ...

s (e.g. metal insulator metal diodes), nor non-linear voltage dependent

resistor A resistor is a passive two-terminal electronic component that implements electrical resistance as a circuit element. In electronic circuits, resistors are used to reduce current flow, adjust signal levels, to divide voltages, bias active e ...

s (i.e. varistors) are currently used with the latter not yet economical, compared to TFT. The

Macintosh Portable The Macintosh Portable is a portable computer that was designed, manufactured, and sold by Apple Computer, Inc. from September 1989 to October 1991. It is the first battery-powered Macintosh, which garnered significant excitement from critic ...

(1989) was perhaps the first consumer laptop to employ an active matrix panel. Since the decline of

cathode-ray tube A cathode-ray tube (CRT) is a vacuum tube containing one or more electron guns, which emit electron beams that are manipulated to display images on a phosphorescent screen. The images may represent electrical waveforms on an oscilloscope, a ...

s, as a consumer display technology, virtually all TVs, computer monitors and smartphone screens that use

LCD A liquid-crystal display (LCD) is a flat-panel display or other electronically modulated optical device that uses the light-modulating properties of liquid crystals combined with polarizers to display information. Liquid crystals do not em ...

OLED An organic light-emitting diode (OLED), also known as organic electroluminescent (organic EL) diode, is a type of light-emitting diode (LED) in which the emissive electroluminescent layer is an organic compound film that emits light in respon ...

technology employ active matrix technology.

References

{{Reflist Display technology

See also

References