Transistor Terminals

 Transistor  terminals:

1.Emitter

2.Base

3.Collector

Emitter:

It is left hand section (or region) of the transistor and its main function is to supply majority charge carriers(electrons in case of NPN transistors and h

oles in case of P-N-P transistors) to the base.The emitter is always forward biased w.r.t base so that it is able to supply majority charge carriers to the base.The emitter is heavily doped so that it may be able to inject a large number of charge carriers.It is of moderate size in order to maintain heavy doping without diluting it or mesh formation in it.

Base:It is the middle section of the transistor and is very lightly doped to reduce the recombination within the base so as to increase collector current and is very thin(of the order of micrometer)in comparison to either emitter or collector so that it may pass most of the injected charge carriers to the collector.

Base form two junctions i.e,emitter junction and collector junction,each having its own barrier voltage.The forward-biased emitter-base junction offers low resistance to the emitter current whereas the collector-base junction,which is reverse biased,offers high resistance to the collector current.As the resistance of emitter-base junction is very small as compared to that of collector-base junction,therefore,the forward bias applied to the emitter-base  junction is usually very small whereas the reverse bias on the collector-base junction is much large.

collector:

It is right hand section of the transistor and its main function is to collect majority charge carriers.Collector is always reverse biased so as to remove the charge carriers away from  its junction with the base.It is moderately doped to avoid the chances of mesh formation even after taking the carriers from the emitter.Large in size to withstand the temperature generated at the collector.