Transistor
- It is a semiconductor device in which one semiconductor either P or N is sandwich between a pair of opposite semiconductor.
- Basically there are two types of transistor: NPN transistor and PNP transistor.
NPN Transistor
- It is a transistor in which N type semiconductor material is sandwiched between P type semiconductors.
PNP transistor
- It is a transistor in which P type semiconductor material is sandwiched between N type semiconductors.
- There are two PN junctions therefore the transistor is regarded as two diodes connected back to back.
- It consists of three terminals namely: Emitter, base and collector.
Emitter
- It supply charge carriers ( Electrons or holes ).
- The emitter is always forward biased with respect to base.
- As the emitter – base is forward biased, its resistance is quite low.
- The emitter is heavily doped as it supplies charge carriers.
Base
- The base is lightly doped and thin because it passes most of charge carriers to collector terminal.
- The base is thinner than the emitter.
Collector
- It collects charge carriers ( Electrons or holes ).
- The collector is always reverse biased with respect to base.
- As the collector – base is reverse biased, its resistance is quite high.
- The collector is moderately doped as it collects charges from base.
- As the most of the heat dissipates through collector, it is wider than the emitter and base terminal.
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