transistor.doc - TRANSISTOR Transistor is a semiconductor...

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TRANSISTOR Transistor is a semiconductor device used to amplify and switch electronic signals. It is composed of a semiconductor material with at least three terminals for connection to an external circuit. A voltage or current applied to one pair of the transistor's terminals changes the current flowing through another pair of terminals. Because the controlled (output) power can be much more than the controlling (input) power, a transistor can amplify a signal. Today, some transistors are packaged individually, but many more are found embedded in integrated circuits . The transistor is the fundamental building block of modern electronic devices , and is ubiquitous in modern electronic systems. Following its release in the early 1950s the transistor revolutionized the field of electronics, and paved the way for smaller and cheaper radios , calculators , and computers , among other things. Symbols PNP NPN Importance The transistor is the key active component in practically all modern electronics . Many consider it to be one of the greatest inventions of the 20th century. Its importance in today's society rests on its ability to be mass produced using a highly automated process ( semiconductor device fabrication ) that achieves astonishingly low per-transistor costs. The invention of the first transistor at Bell Labs was named an IEEE Milestone in 2009
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Usage The bipolar junction transistor (BJT) was the most commonly used transistor in the 1960s and 70s. Even after MOSFETs became widely available, the BJT remained the transistor of choice for many analog circuits such as simple amplifiers because of their greater linearity and ease of manufacture. Desirable properties of MOSFETs, such as their utility in low-power devices, usually in the CMOS configuration, allowed them to capture nearly all market share for digital circuits; more recently MOSFETs have captured most analog and power applications as well, including modern clocked analog circuits, voltage regulators, amplifiers, power transmitters and motor drivers. The essential usefulness of a transistor comes from its ability to use a small signal applied between one pair of its terminals to control a much larger signal at another pair of terminals. This property is called gain . A transistor can control its output in proportion to the input signal; that is, it can act as an amplifier . Alternatively, the transistor can be used to turn current on or off in a
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