Hitachi IGBT Module Application Manual
Figure 2. Structure of IGBT die
Symbol and Equivalent Circuit
An IGBT module is essentially a switching transistor controlled by the voltage applied to its gate
terminal. Figure 3 shows the symbol and equivalent circuit of an IGBT module.
Figure 3. IGBT Symbol and Equivalent Circuit
Operational Switching Description
For IGBT turn-ON, the N-channel MOSFET is turned ON by first applying a positive voltage to gate-
emitter electrode (see Figure 3). As a consequence, all of the MOSFET’s drain current flows as the base
current of the pnp transistor, so this transistor turns ON and the IGBT reaches its ON state.
For IGBT turn-OFF, a zero or minus bias must be applied as the gate-emitter voltage so that the
MOSFET’s current and the base current of the transistor will be cut off, thus causing the IGBT to reach an
Since an IGBT is comprised of MOSFET and pnp transistor
structures, it is inherently able to reduce its ON state conduction
loss, due mainly to the phenomenon of conductivity modulation.