Transistor
Category : JEE Main & Advanced
(1) The name of this electronic device is derived from it's fundamental action transfer resistor.
(2) Transistor does not need any heater or hot filament, transistor is small in size and light in weight.
(3) Transistor in general is known as bipolar junction transistor.
(4) Transistor is a current operated device.
(5) It consists of three main regions
(i) Emitter (E) : It provides majority charge carriers by which current flows in the transistor. Therefore the emitter semiconductor is heavily doped.
(ii) Base (B) : The based region is lightly doped and thin.
(iii) Collector (C) : The size of collector region is larger than the two other regions.
(6) Junction transistor are of two types :
(i) NPN transistor : It is formed by sandwiching a thin layer of P-type semiconductor between two N-type semiconductors
In NPN transistor electrons are majority charge carriers and flow from emitter to base.
(ii) PNP transistor : It is formed by sandwiching a thin layer of N-type semiconductor between two P-type semiconductor
In PNP transistor holes are majority charge carriers and flow from emitter to base.
In the symbols of both NPN and PNP transistor, arrow indicates the direction of conventional current.
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