Field-effect transistor - Wikipedia, the free encyclopedia

Field-effect transistor - Wikipedia, the free encyclopedia...

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 Field-effect transistor From Wikipedia, the free encyclopedia (Redirected from Field effect transistor ) Jump to: navigation , search High-power N-channel field-effect transistor The field-effect transistor (FET) is a type of transistor that relies on an electric field to control the shape and hence the conductivity of a 'channel' in a semiconductor material. The concept of the field effect transistor predates the bipolar junction transistor (BJT), though it was not physically implemented until after BJTs, due to the limitations of semiconductor materials and relative ease of manufacturing BJTs compared to FETs at the time.
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Contents 1 Termin als 2 Compo sition 3 Types of field- effect transist ors 4 FET operati on 5 Uses 6 Referen ces 7 See also 8 Externa l links [ edit ] Terminals All FETs except J-FETs have four terminals, which are known as the gate , drain , source and body/base/bulk/ substrate . Compare these to the terms used for BJTs: base , collector and emitter . BJTs and J-FETs have no body terminal. Cross Section of an n-type MOSFET The names of the terminals refer to their functions. The gate terminal may be thought of as controlling the opening and closing of a physical gate. This gate permits electrons to flow through or blocks their passage by creating or eliminating a channel between the source and drain. Electrons flow from the source terminal towards the drain terminal if influenced by an applied voltage. The body simply refers to the bulk of the semiconductor in which the gate, source and drain lie. Usually the body terminal is connected to the highest or lowest voltage within the circuit, depending on type. The body terminal and the source terminal are sometimes connected together since the source is also sometimes connected to the highest or lowest voltage
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within the circuit, however there are several uses of FETs which do not have such a configuration, such as transmission gates and cascode circuits. [ edit ] Composition The FET can be constructed from a number of semiconductors, silicon being by far the most common. Most FETs are made with conventional bulk semiconductor processing techniques , using the single crystal semiconductor wafer as the active region, or channel. Among the more unusual body materials are amorphous silicon , polycrystalline silicon or other amorphous semiconductors in thin-film transistors or organic field effect transistors that are based on organic semiconductors and often apply organic gate insulators and electrodes. [ edit ] Types of field-effect transistors Depletion-type FETs under typical voltages. JFET, poly-silicon MOSFET, double-gate MOSFET, metal- gate MOSFET, MESFET. depletion , electrons , holes , metal , insulator . Top=source, bottom=drain, left=gate, right=bulk. Voltages that lead to channel formation are not shown The channel of a FET (explained below) is doped to produce either an N-type semiconductor or a P-type semiconductor . The drain and source may be doped of opposite type to the channel, in the case of
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Field-effect transistor - Wikipedia, the free encyclopedia...

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