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What is an Active Matrix?

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  • Written By: Solomon Branch
  • Edited By: Jenn Walker
  • Last Modified Date: 15 November 2016
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    Conjecture Corporation
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Active matrix is a technology used in the flat panel liquid crystal displays of notebook and laptop computers. This technology provides a more responsive image at a wider range of viewing angles than passive matrix displays. Manufacturers of laptops and notebooks prefer active matrix displays, also referred to as active matrix liquid crystal display (AMLCD) or thin film transistor (TFT), because they have a high-quality image, a wide array of colors, a fast response time and are very low in weight. They also consume less power, a trait that is desirable in portable devices.

There are two basic types of displays: active matrix and passive matrix. Passive matrix is the older, simpler technology and has a much slower response time than active matrix screens. Due to the way the signal is processed in passive matrix, the voltage control is also imprecise. This creates a fuzzy image with a noticeable lack of contrast.

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In active matrices, TFTs are used to create the screen. TFTs are basically tiny capacitors and switching transistors that are more dynamic than the integrated circuits used in passive matrix. This technology allows for more precise control over the voltage used to charge the screen. This in turn allows the pixels, the tiny dots on a display that are charged to create an image, to allow less light through so that the image created has more contrast. Along with the faster response time, active matrix screens have a more definitive image and a more dynamic picture because the image can refresh at a faster rate than passive matrix .

In practical terms, you can see the difference in passive and active matrices when using a mouse pointer. When moving the pointer across the screen in a passive matrix type display, the image will have “trailers,” or double images, moving across the screen behind the pointer. The pointer will also have a fuzzier image with little contrast. In active matrices, moving the mouse pointer does not produce “trailers,” and the image is sharper.

The term "active matrix" was reportedly first used by Dr. Peter Brody in 1975. He used the term to describe a method of switching the individual elements of a flat panel display using a cadmium selenide (CdSe) TFT for each pixel. Although TFTs are still used today as the primary building block for active matrix screens, diodes can also be used.

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