IGBT ( Insulated Gate Bipolar Transistor )
IGBT stands for insulated gate bipolar transistor. It is having the advantages of both power MOSFET and BJT. In IGBT layer is P is used as a substrate. One side is deposited with metal layer to form collector and other side of P substrate N layer is epitaxial grown. The other layers are same as power MOSFET. The three terminals of IGBT are emitter E gate G and collector C .
figure IGBI Basic structure symbol
The IGBT is a four layer N-P-N-P device with an MOs gated channel connecting the 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. TGBT maintains gate control over a wide range of anode current and voltage. The basic structure of the IGB is shown in figure.
In many respect s it is similar to a power MOSFET main difference is the presence of P+ as injecting layer. Next is N+ layer. There is a P_N junction between these layers and two more junctions ( J2 and J3) .