Difference Between BJT and IGBT

BJT (Bipolar Junction Transistor) and IGBT (Insulated Gate Bipolar Transistor) are two types of transistors used to control currents. Both devices have PN junctions and different in device structure. Although both are transistors, they have significant differences in characteristics.

BJT (Bipolar Junction Transistor)

BJT is a type of transistor that consists of two PN junctions (a junction made by connecting a p type semiconductor and n type semiconductor). These two junctions are formed using connecting three semiconductor pieces in the order of P-N-P or N-P-N. Therefore two types of BJTs, known as PNP and NPN, are available.

Three electrodes are connected to these three semiconductor parts and middle lead is called ‘base’. Other two junctions are ‘emitter’ and ‘collector’.

In BJT, large collector emitter (I_c) current is controlled by the small base emitter current (I_B), and this property is exploited to design amplifiers or switches. Therefore, it can be considered as a current driven device. BJT is mostly used in amplifier circuits.

IGBT (Insulated Gate Bipolar Transistor)

IGBT is a semiconductor device with three terminals known as ‘Emitter’, ‘Collector’ and ‘Gate’. It is a type of transistor, which can handle a higher amount of power and has a higher switching speed making it high efficient. IGBT has been introduced to the market in 1980s.

IGBT has the combined features of both MOSFET and bipolar junction transistor (BJT). It is gate driven like MOSFET and has current voltage characteristics like BJTs. Therefore it has the advantages of both high current handling capability, and ease of control. IGBT modules (consists of a number of devices) handle kilowatts of power.