Bipolar transistor: Difference between revisions
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{{Image|Planar bipolar transistor.PNG|right|200px|A planar bipolar junction transistor as might be constructed in a [[integrated circuit]].}} | {{Image|Planar bipolar transistor.PNG|right|200px|A planar ''npn'' bipolar junction transistor as might be constructed in a [[integrated circuit]].}} | ||
In [[electronics]], the '''bipolar transistor''', more completely the '''bipolar junction transistor''', is a three terminal [[semiconductor|semiconductor device]] used for switching and amplification. In concept it consists of two back-to-back [[Semiconductor diode|''pn''-diodes]], forming either a ''pnp'' or an ''npn'' sandwich, where ''p'' refers to semiconductor doped to produce positively charge carriers (holes) and ''n'' refers to semiconductor doped to provide negatively charged carriers (electrons). However, the center region is thin enough to allow carriers injected from one of the end layers (the ''emitter'' ''E'') to actually ''diffuse'' across the center region (the ''base B'') and be collected by the other end region (the ''collector C''). | In [[electronics]], the '''bipolar transistor''', more completely the '''bipolar junction transistor''', is a three terminal [[semiconductor|semiconductor device]] used for switching and amplification. In concept it consists of two back-to-back [[Semiconductor diode|''pn''-diodes]], forming either a ''pnp'' or an ''npn'' sandwich, where ''p'' refers to semiconductor doped to produce positively charge carriers (holes) and ''n'' refers to semiconductor doped to provide negatively charged carriers (electrons). However, the center region is thin enough to allow carriers injected from one of the end layers (the ''emitter'' ''E'') to actually ''diffuse'' across the center region (the ''base B'') and be collected by the other end region (the ''collector C''). | ||
Revision as of 14:25, 10 June 2011
A planar npn bipolar junction transistor as might be constructed in a integrated circuit.
In electronics, the bipolar transistor, more completely the bipolar junction transistor, is a three terminal semiconductor device used for switching and amplification. In concept it consists of two back-to-back pn-diodes, forming either a pnp or an npn sandwich, where p refers to semiconductor doped to produce positively charge carriers (holes) and n refers to semiconductor doped to provide negatively charged carriers (electrons). However, the center region is thin enough to allow carriers injected from one of the end layers (the emitter E) to actually diffuse across the center region (the base B) and be collected by the other end region (the collector C).
Very small changes in the emitter-base junction voltage have an exponential influence over the number of carriers injected from the emitter, and so the base has enormous control over the current diffusing across the base to the collector. Moreover, the current consumed by the base in normal operation is very small, so the device serves well to amplify either a current or a voltage signal applied to the base.
History
The bipolar transistor was the historically first transistor invented. Prior to its invention in 1947 by Bardeen, Brattain and Shockley at Bell Laboratories, semiconductor devices were only two-terminal devices, like diodes and rectifiers. More of the history and development of this device can be found in an historical article by Shockley[1] and a more recent history.[2]
References
- ↑ WS Shockley (1976). "The path to the conception of the junction transistor". IEEE Trans Electron Dev. ED-23: pp. 597 ff.
- ↑ M Riordan & L Hoddeson (1997). Crystal fire: the birth of the information age. W. W. Norton & Company. ISBN 0393041247.