NPN transistor


The most commonly used transistor configuration is the NPN Transistor.
In this, we used common emitter configuration of NPN Transistors.


The transistor has three regions, namely ; emitter, base and collector. The base is much
thinner than the emitter while collector is wider than both as shown. However, for the sake of convenience, it is customary to show emitter and collector to be of equal size.The emitter is heavily doped so that it can inject a large number of charge carriers (electrons
or holes) into the base.
  •  The base is lightly doped and very thin ; it passes most of the emitter injected
charge carriers to the collector. The collector is moderately doped
The resistance of emitter diode (forward biased) is very small as compared to collector diode (reverse biased). Therefore, forward bias applied to the emitter diode is generally very small whereas reverse bias on the collector diode is much higher.
           





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