IGBT stand for insulated gate bipolar transistor. It is having the advantage of both power MOSFET and BJT. In IGBT, layer P is used as a substrate. One side is deposited with a metal layer to form a collector and another side of the P substrate, N layer is epitaxially grown. The other layer is the same as power MOSFET. The three-terminal of IGBT are Emitter E, Gate G, and collector C.
The IGBT is a four-layer N-P-N-P device with a MOS gated channel connecting two N-type regions. It is a new high conductance MOS gate controlled power switch. In operation of IGBT, the epitaxial region is conductivity modulated and thereby eliminating a major component of the on resistance.
IGBT maintains gate control over a wide range of anode current and voltage. The basic structure of the IGBT is shown in the figure.
In many respects, it is similar to a power MOSFET. The main difference is the presence of P as the injecting layer. Next is the N layer. There is a P-N junction between this layer and more junction as shown in the figure. IGBTs are widely used in medium power application such as Dc and AC motor drive UPS system, power supplies for solenoids, relays, and contractors. Though IGBTs are more expensive than BJTs, they have lower gate drive requirements, lower switch losses.