Transistor : Emitter, Base and Collector

  • 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

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. 

structure and symbol of the transistor

  • 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.

  • The base is lightly doped and thin because it passes most of charge carriers to collector terminal. 
  • The base is thinner than the emitter.

  • 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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