Test: IGBTs - Electrical Engineering (EE) MCQ

Like MOSFET IGBT possess high input impedance.

Low on state power loss is one of the best parameters of both BJT & the IGBT.

IGBT is a three terminal device. It has a gate, a emitter & a collector.

 It is called as a injection layer, because it injects holes into the n^– layer.

The controlling parameter is the gate to emitter voltage, as the device is a voltage controlled device.

 It is called as the drift layer because its thickness determines the voltage blocking capabilities of the device.

 The drift layer which is a n^– layer determines the voltage blocking capabilities.

The controlling parameter is the gate to collector current.

The IGBT is a semiconductor device with four alternating layers (P-N-P-N) that are controlled by a metal-oxide-semiconductor (MOS) gate structure without regenerative action.

The earlier IGBT’s had latch-up problems (device cannot turn off even after the gate signal is removed), and secondary breakdown problems (in which a localized hotspot in the device goes into thermal runaway and burns the device out at high currents).

After latch-up the collector emitter current is no longer in control of the gate terminal.

 Forced commutation of current is the only way to turn off a latched up IGBT.

V-I curves are plotted for Ic vs Vce with the controlling parameter (Vge) as a parameter.

Latch up occurs when the current through the device (Ic) collector current increases beyond a certain value.

Vce decreases from 0.9 to 0.1 of the initial value whereas others increase.

Due to its high gate impedance, IGBTs require less gate drive current.

Gate of the MOSFET forms the gate terminal of the IGBT, the source of MOSFET is connected to the base of the BJT and drain to the collector.

All of the above mentioned are alternate names of IGBTs.

IGBT has a p-n-p structure with fingers of n⁺ layers into the p layer. The p layer has the largest cross section and forms the body of the IGBT.

All of the above mentioned can be used but Si-Ca has certain advantages over the other materials.