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) .