An IGBT is a device suitable for high-current control combining a voltage-driven MOSFET in the front stage and a transistor allowing a large current to flow in the rear stage.
IGBT：Insulated Gate Bipolar Transistor
[Equivalent circuit and operation details]
- The equivalent circuit of the IGBT is shown in Fig. 3-13 (b). The RBE value is set so that the NPN Tr does not turn on.
- Applying ON signal to gate of an Nch MOSFET turns on conduction state.
- As a result, current flows from the emitter to the base of PNP Tr. This base current works to lower the ON resistance of Nch MOSFET. (Conductivity modulation effect)
[Comparison with MOSFET]
- Gate driving operation is the same as Nch MOSFETs.
- In ON state, decrement of ON resistance of Nch MOS enables high current flow.
- Voltage drop across the emitter and base of PNP Tr occurs in the entire current region.(Approximately 1.0 V is added up as ON voltage.)