Transistor - An Overview

A transistor is a semiconductor device used to amplify and switch electronic signals and electrical power. It is composed of semiconductor material with at least three terminals for connection to an external circuit.
A transistor is a three terminal semiconductor device.  It  consists of three terminals and two PN junctions.  Transistors have revolutionized the field of computing and telecommunications. Transistors are used to amplify signal.  They can be used two switch power on and off.  

The invention of the Transistor enabled the production of cheaper radios, calculators and computers.  

The transistor consists of two PN junctions.  It consists of two P materials with a N type materials sandwiched in between which is called a PNP transistor or two N-type materials with a P-type material sandwiched in between which is called a NPN transistor.  Thus, two PN junctions are formed.  

The transistor consists of three terminals as mentioned earlier.  The terminal attached to the material in the centre is called the Base.  The terminals attached to the other two materials in the sides are called the emitter and the collector.

The common transistor is also known as the Bipolar transistor.