What are the advantages of Insulated gate bipolar transistor (IGBT)?

#Technical studies -study 12

Introduction

We know that both MOSFETs and BJTs are used in switching applications.  BJTs have advantages of lower conduction loss and MOSFETs have the advantage of high switching speed. Insulated gate bipolar transistor is a hybrid semiconductor device. IGBT is constructed using both the advantages of BJT and MOSFET. Therefore it becomes an ideal switch.

It has three terminals namely: – gate, collector, emitter

Below there is a structure of an IGBT.

IGBT Structure
IGBT Equivalent circuit
IGBT Symbol 1

It is a normally off device. Gate voltage controls the current between collector and emitter.

IGBT Symbol 2

IGBTs are available in two versions

  • Punch through
  • Non punch through

Punch through IGBT has an n+ buffer layer between its p+ and n- regions. It has a negative temperature coefficient. This device has the advantage of high switching speeds.

While Non punch through IGBT has no n+ layer but has high conduction power than punch through device. It has a positive temperature coefficient that makes this suitable for paralleling.

Advantages of IGBT:

  • Lower conduction compared to MOSFET.
  • Higher input impedance compared to BJT.
  • Simple gate driven.
  • Collector emitter breakdown voltage is higher
  • Suitable for high voltage and current applications in moderate frequency.

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