ECE 442 Power Electronics 1

IGBT: Insulated-Gate Bipolar Transistor

• Combination BJT and MOSFET– High Input Impedance (MOSFET)– Low On-state Conduction Losses (BJT)

• High Voltage and Current Ratings

• Symbol

ECE 442 Power Electronics 2

Cross-Sectional View of an IGBT

Metal

Silicon Dioxide

Metal

ECE 442 Power Electronics 3

IGBT Equivalent Circuit for VGE<VT

+

VCCIEPNP

ICPNP

IBPNP

ICNPN

IENPN

IBNPN

Leakage Current

IRBE

Both transistors are OFF

ECE 442 Power Electronics 4

IGBT Equivalent Circuit for VGE>VT

+

VCC

NPN Transistor becomes forward biased at the BE, drawing current from the Base of the PNP transistor.

MOS transistor conducts, drawing current from the Base of the PNP transistor.

PNP transistor turns ON,

RMOD decreases due to carrier injection from the PNP Emitter.

ECE 442 Power Electronics 5

Channel is Induced When VGE>VT

Induced Channel

electrons

RMOD PNP

RBE

NPN

ECE 442 Power Electronics 6

IGBT Output Characteristics

Follows an SCR characteristic

ECE 442 Power Electronics 7

IGBT Transfer Characteristic

ECE 442 Power Electronics 8

IGBT Used as a Switch

ECE 442 Power Electronics 9

Fairchild FGA25N120AND IGBT

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