Insulated Gate Bipolar Transistor

Insulated Gate Bipolar Transistor

An IGBT combines the advantages of BJTs and MOSFETs. An IGBT [1]has high input impedance like MOSFETs, and low on-state conduction losses, like BJTs. But there is no second breakdown problem, as with BJTs. The performance of an IGBT is closer to that of a BJT than an MOSFETs. This is due to the p⁺ substrate, which is responsible for the minority carrier injection into the n-region.

V-I characteristics of IGBT

The diagram below shows the V-I characteristics of an IGBT. The controlling parameter is gate-emitter voltage because it is a voltage controlled device. When positive supply is provided to gate terminal, an IGBT turns on by opening the channel for n carriers and is turned off by removing the gate voltage to close the channel

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Application of IGBT

IGBTS are widely used in medium power applications such as dc and ac motor drives, ups, power supplies and drives for solenoids, relays, and contactors. Though IGBTS ar somewhat more expensive than BJTS yet they are being popular because of the lower gate drive requirements, lower switches loss and smaller snubber circuit requirement.

Comparison of IGBT with MOSFET

The number ofp-njunctions

MOSFETshave onep-njunction andIGBTshave twop-njunctions.

Maximum Voltage

Comparatively,MOSFETscannot handle voltages as high as those handled by an IGBT andIGBTshave the ability to handle higher voltages since they have an additional region.

Switching Times

Switching times forMOSFETsare comparatively faster than IGBTS.

References

[1] H.Rashid, Muhammad.IGBT. India: PEARSON PUBLICATION, 2013.