A Transistor is an electronic device that replaced the bulky and high power consuming devices called vaccum triodes.
NPN-P type is sandwiched between n.
Construction of Transistor
-One side of transister and always heavily doped and supplies charge carriers.
-Middle region of the transistor.Lightly doped than other two.
-Region situated opposite to emitter.Collects the charge carriers that cross the base region after emanating from the emitter.
-PN junction formed by the emitter and base.
-PN junction formed by the collector and base.
-Two depletion regions formed around collector and emitter.
-No currents flows when there is no supply.
-When two junctions are biased using external DC supply.
-It has 3 modes of operation.