Active matrix is a type of addressing scheme

Addressing scheme

There are three different addressing schemes for display devices: direct, matrix, and raster. The purpose of each scheme is to set the state of a pixel to either black/white or, more commonly, a gray-scale level.-Direct addressing:...

 used in flat panel displays. The term describes a method of switching individual elements of a flat panel display

Flat panel display

Flat panel displays encompass a growing number of electronic visual display technologies. They are far lighter and thinner than traditional television sets and video displays that use cathode ray tubes , and are usually less than thick...

, using a CdSe

Cadmium selenide

Cadmium selenide is a solid, binary compound of cadmium and selenium. Common names for this compound are cadmium selenide, cadmium selenide, and cadmoselite ....

 or Silicon

Silicon

Silicon is a chemical element with the symbol Si and atomic number 14. A tetravalent metalloid, it is less reactive than its chemical analog carbon, the nonmetal directly above it in the periodic table, but more reactive than germanium, the metalloid directly below it in the table...

-based thin-film transistor

Thin-film transistor

A thin-film transistor is a special kind of field-effect transistor made by depositing thin films of a semiconductor active layer as well as the dielectric layer and metallic contacts over a supporting substrate. A common substrate is glass, since the primary application of TFTs is in liquid...

 (TFT) for each pixel

Pixel

In digital imaging, a pixel, or pel, is a single point in a raster image, or the smallest addressable screen element in a display device; it is the smallest unit of picture that can be represented or controlled....

. The technology was invented and first demonstrated by T Peter Brody

T Peter Brody

T. P. "Peter" Brody , was a British-naturalised physicist and the inventor of Active Matrix Thin-Film Transistor display technology, having produced the world's first Active Matrix Liquid Crystal Display in 1972 and the first functional AM-EL in 1973 while employed by Westinghouse Electric...

 and his Thin-Film Devices department at Westinghouse Electric Corporation in 1968, and the term was introduced into the literature in 1975.

Given a m × n matrix, the number of connectors needed to address the display is m + n. Each pixel

Pixel

In digital imaging, a pixel, or pel, is a single point in a raster image, or the smallest addressable screen element in a display device; it is the smallest unit of picture that can be represented or controlled....

 is attached to a switch-device, which actively maintains the pixel state while other pixels are being addressed, which also prevents crosstalk from inadvertently changing the state of an unaddressed pixel. The most common switching devices are Thin Film Transistors (TFT), i.e. a FET based on either the cheaper non-crystalline thin-film silicon

Silicon

Silicon is a chemical element with the symbol Si and atomic number 14. A tetravalent metalloid, it is less reactive than its chemical analog carbon, the nonmetal directly above it in the periodic table, but more reactive than germanium, the metalloid directly below it in the table...

 (a-Si

Amorphous silicon

Amorphous silicon is the non-crystalline allotropic form of silicon. It can be deposited in thin films at low temperatures onto a variety of substrates, offering some unique capabilities for a variety of electronics.-Description:...

), polycrystalline

Polycrystalline

Polycrystalline materials are solids that are composed of many crystallites of varying size and orientation. The variation in direction can be random or directed, possibly due to growth and processing conditions. Fiber texture is an example of the latter.Almost all common metals, and many ceramics...

 silicon (poly-Si

Polycrystalline silicon

Polycrystalline silicon, also called polysilicon, is a material consisting of small silicon crystals. It differs from single-crystal silicon, used for electronics and solar cells, and from amorphous silicon, used for thin film devices and solar cells....

), or CdSe

Cadmium selenide

Cadmium selenide is a solid, binary compound of cadmium and selenium. Common names for this compound are cadmium selenide, cadmium selenide, and cadmoselite ....

 semiconductor

Semiconductor

A semiconductor is a material with electrical conductivity due to electron flow intermediate in magnitude between that of a conductor and an insulator. This means a conductivity roughly in the range of 103 to 10−8 siemens per centimeter...

 material.

Another variant is to use diodes or resistors, but neither diode

Diode

In electronics, a diode is a type of two-terminal electronic component with a nonlinear current–voltage characteristic. A semiconductor diode, the most common type today, is a crystalline piece of semiconductor material connected to two electrical terminals...

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

Resistor

A linear resistor is a linear, passive two-terminal electrical component that implements electrical resistance as a circuit element.The current through a resistor is in direct proportion to the voltage across the resistor's terminals. Thus, the ratio of the voltage applied across a resistor's...

s (i.e. varistor

Varistor

A varistor is an electronic component with a "diode-like" nonlinear current–voltage characteristic. The name is a portmanteau of variable resistor...

s) are currently used. The latter of these is not yet economical when compared to TFT.

See also

• AMLCD
• AMOLED
• TFT-LCD
• Passive matrix addressing
  Passive matrix addressing
  Passive matrix addressing is an addressing scheme used in earlier LCD displays, and may be used in future LCD displays. This is a matrix addressing scheme meaning that only m + n control signals are required to address a m × n display...
  
  
• Pixel geometry
  Pixel geometry
  The components of the pixels in an image sensor or display can be ordered in different patterns, called pixel geometry....
  
  
• LCD