Bipolar Junction Transistor

Transistors are one of the largely used semiconductor devices which are used for wide variety of applications including amplification and switching The word  Transistor derived from  combination of the two words Transfer Varistor which describes their mode of operation There are two basic types of bipolar transistor construction, PNP and NPN, which is based on the physical arrangement of the P-type and N-type semiconductor materials from which they are made.