Construction of Bipolar Junction Transistor (BJT)

CONSTRUCTION OF BIPOLAR JUNCTION TRANSISTOR

A Bipolar junction transistor has three regions known as emitter, base and collector. All these three regions are provided with terminals, which are labeled as E(emitter), B (Base) and C (collector) respectively. It is shown in fig.3.33.

Emitter:

It is a region situated in one side of transistor, which supplies charge carries to the other two regions. The emitter is a heavily doped region.

Base:

It is the middle region that forms two PN junctions in the transistor. The base of transistor is thin as compared to the emitter and is a lightly doped region.

Collector:

It is a region situated in the other side of transistor, which collects charge carriers. The collector of a transistor is always larger than the emitter and base. The doping level of the collector is intermediate between the heavy doping emitter and the light doping of the base.

The transistor has two P-N junction one junction is between the emitter and the base, it is called as Emitter-Base junction (or) emitter junction (JE). The other junction is between the base and collector, it is called as collector-base junction (or) collector junction (JC). The transistor is like two P-N junction connected back to back it is shown in fig.3.34 (a) & (b).