Transistor

Transistor is the crystal which three doped crystal like N P and N.

There are mainly three terminal they are

a)Emitter(E)

It is heavily doped part of the transistor.Its main task is to carry majority charge carrier. It denoted by symbol E.

b)Base(B)

Middle part of transistor called base.It is very thin part of its.As compare to other region it is 10^-6m thin. Its main task is to pass the majority charged carrier from emitter to collector.It is very lightly doped to minimized the reunion of free electron and holes. Its denoted by the symbol B.

c)Collector(C)

It is the last or third region of the transistor. It is moderately doped region. Its task is to collect the majority charge carrier endow by emitter and pass through base. Mainly this region is physically larger than other region because to evaporate the greater heat generated in the collector.

There are two type of transistor they are:-

1)N-P-N Transistor
It is the transistor formed by growing a thin layer of p type crystal between two layer of N type crystal. In the NPN Transistor free electron are the majority charge carrier in the emitter and collector in other hand holes are the majority charge carrier in the base.

Working process of N-P-N Transistor

The circuit diagram of NPN transistor is shown in figure. Here battery VBE acts as forward bias and reverse bias by battery VCB to the transistor. When collector base junction is forward bias then VBE>0.7V for silicon and 0.3V for germanium. Then hole act majority charge carrier in N type flow from emitter  toward the P type base resulting the flow of current through the emitter known as emitter current Ie. The base is thin and likely doped as compared to emitter and collector. Thud 5%of the hole recombined with the electron in the base region resulting the flow of current through the base known as base current Ib.The majority of hole 95% enter into the collector region. The flow of this electron in the collector region called collector current Ic. The electron in the collector region attract toward the positive terminal of the battery VCB and recombined at the same time and equal number of electron entre the emitter regions from the negative terminal of the battery VBE.

2)P-N-P Transistor

It is the exactly opposite to the NPN transistor. We have already learn the function or working process of  NPN transistor. It is the transistor formed by growing of thin layer of N type crystal between two P type of crystal.In the PNP Transistor free electron are the majority charge carrier in the base in other hand holes are the majority charge carrier in the collector and emitter.

Working process of P-N-P Transistor

We have already said that it is exactly opposite to the NPN transistor,The circuit diagram or figure also clearly show that. The circuit diagram of PNP transistor is shown in figure. Here battery VBE acts as reverse bias and forward  bias by battery VCB to the transistor. When collector base junction is reverse bias then VBE>0.7V for silicon and 0.3V for germanium. Then hole act majority charge carrier in P type flow from emitter  toward the N type base resulting the flow of current through the collector known as collector current Ic. The base is thin and likely doped as compared to emitter and collector. Thud 5%of the hole recombined with the electron in the base region resulting the flow of current through the base known as base current Ib.The majority of hole 95% enter into the emitter region. The flow of this electron in the emitter region called emitter current Ie. The electron in the emitter region attract toward the positive terminal of the battery VCB and recombined at the same time and equal number of electron entre the collector regions from the negative terminal of the battery VBE.