Transistor

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Common transistor

Information

A transistor is a active component, one of the most important in use. Being active means that it amplifies a signal without distortion being worth mentioning. A transistor can control a large electric current using a small current. One type is the bipolar (junction) transistor, this is a three-terminal device constructed of doped semiconductor material and may be used in amplifying or switching applications. Bipolar transistors are so named because their operation involves both electrons and holes.

With NPN transistors a small current entering the base in common-emitter mode is amplified in the collector output. In other terms, an NPN transistor is "on" when its base is pulled high relative to the emitter. With PNP transistors a small current leaving the base in common-emitter mode is amplified in the collector output. In other terms, a PNP transistor is "on" when its base is pulled low relative to the emitter.