What is transistor & How transistor working


Transistor is an electronic device and its  made of semiconductor material. mostly silicon used as a semiconductor material. transistor having many uses. transistor act as  a switch, voltage regulation process, modification of signals, amplification of signals. when N-type  or P-type semiconductor  is connected between two P-type or N- type semiconductor then its look like two PN junction diode. such device is called transistor.

The transistor having three layer, three terminal and two PN  junction diode. the three layer of transistor are,

  1. Base
  2. Emitter
  3. Collector

Types of Transistor:

There are two types of transistor available. They are given below,

  1. NPN transistor
  2. PNP transistor


NPN Transistor:

The NPN transistor having connected between two N channel and P channel semiconductor materials. NPN transistor also called negative positive and negative transistor. Its formed like adding diode in back to back connection. in NPN transistor the majority carrier is electrons. the current flow in NPN transistor is collector to emitter terminal. positive voltage is applied to collector base junction  and negative voltage is applied in emitter base junction.

PNP Transistor :

The PNP transistor having connected between two P channel and N channel semiconductor material. PNP transistor also called positive negative and positive transistor. Its formed like adding diode in back to back connection. PNP transistor the majority carrier is holes. the current flow in PNP transistor is emitter to collector terminal. positive voltage is applied to emitter base junction and negative voltage is applied in collector base junction.

Working of Transistor:

The working of transistor is consists of three major terminals, that is base, emitter and collector. and  two major junctions are emitter base junction and collector base junction. the emitter base junctions consists of forward bias and collector base junction consists of reverse bias. the below diagram will show the working of transistor.


The small current is applied to base terminal. the small current will cause the electrons move to collector region. the few electrons of emitter joint together with base holes. the rest of the electrons are move to collector region. so the large current can flow in the collector region. the current flow from collector to emitter can control by varying the base current.

Transistor working in these 3 major region.

  1. Active Region
  2. saturation region
  3. cutoff region

Active region mostly used for transistor in amplifier purposes

Saturation region is mostly used for transistor act as switching device, in this region transistor working as  ON switch condition.

Cutoff region is mostly used for transistor act as a switching device and in this region transistor working as closed switch.

Advantages of Transistor:

  1. compact design and less weight
  2. switching operation 1000 times per second
  3. operating efficiency is very high
  4.  life time also very long
  5. low cost.


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