A FET [ Field Effect Transistor] is a voltage controlled device ,the output characteristics are controlled by input voltage (i.e. electric field) and not by input current. FETs are also known as unipolar transistors .There are two basic types of field effect transistors :
1.Junction Field Effect Transistor ( JFET )
2.Metal oxide semiconductor Field Effect Transistor (MOSFET) and the improve form of jfet.