IGBT｜Basic
IGBT Structure
2023.07.19
Points of this article
・As basic knowledge, it is important to understand the structure of IGBTs and its relation to the equivalent circuit.
As explained in “About IGBTs“, IGBTs are power transistors that, by combining aspects of MOSFETs and bipolar transistors, offer advantages specific to both. Here the basic structure of these devices is explained for the example N-channel IGBTs, which are currently the mainstream. Below, references to IGBTs generally assume N-channel devices.
IGBT Structure
We begin by reviewing the circuit symbol, a simple equivalent circuit, and the basic operation of IGBTs, in order to facilitate an understanding of their structure as a semiconductor device.
An IGBT has three terminals–the gate, collector, and emitter. The gate can be considered to be like the gate of a MOSFET, and the collector and emitter can be regarded as similar to those of a bipolar transistor. Like a MOSFET, an IGBT is a voltage-controlled device; in the case of an N-channel IGBT, when a gate voltage VGE that is positive with respect to the emitter is applied, there is conduction between the collector and the emitter, and a collector current IC flows.
Below are shown a schematic diagram (cross-sectional diagram) showing the structure of an IGBT as a semiconductor device, as well as the equivalent circuit. The diagrams are simplified to aid understanding. The blue arrow represents the flow of the collector current IC. Please compare the structure diagram with the equivalent circuit diagram.
As shown in the diagram of the device structure, a P+ collector layer is formed on the drain side in an N-channel MOSFET, and the structure from the collector to the emitter is a stack of P type-N type-P type-N type layers.
The N-channel MOSFET drain and PNP transistor base in the equivalent circuit are common, and constitute the N- drift layer of the IGBT. The gate is a thin film conductor on an insulating film; the gate of the N-channel MOSFET is the IGBT gate. The IGBT emitter is an N+ layer, and corresponds to the source of the N-channel MOSFET. The collector of the PNP transistor is a P+ layer which forms a junction with the IGBT emitter N+ layer. The emitter of the PNP transistor is a P+ layer, and serves as the IGBT collector.
Although this is all somewhat complicated, the reader should understand that the structure of the IGBT, represented schematically, is as shown in the equivalent circuit.
【Download Documents】 Basics of IGBTs
IGBTs are one of the typical power devices and are used in a wide range of applications including motor drives. This handbook provides a basic understanding of IGBTs, including their application scope and application picture based on their features, their structure and principle of operation, and how they compare with and use other power devices.
IGBT
Basic
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About IGBTs
- Applications Using IGBTs
- IGBT Structure
- Principles of Operation of IGBTs
- Range of Application of IGBTs
- IGBT Features: Comparisons with MOSFETs and Bipolar Transistors
- Selective Use of Power Devices in Motor Applications
- Short Circuit Withstand Time (SCWT) of IGBTs
- IGBTs Incorporating Fast Recovery Diodes (FRDs)
- About IGBT IPMs （Intelligent Power Modules）
Application
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IGBT IPM: Protection Functions and Operation Sequences
- Short Circuit Current Protection (SCP) Function of IGBT IPMs
- Control Power Supply Undervoltage Lockout（UVLO) Function of IGBT IPMs
- Thermal shutdown（TSD） Function of IGBT IPMs
- Analog Temperature Output（VOT）of IGBT IPMs
- Fault Output（FO）of IGBT IPMs
- Control inputs （HINU, HINV, HINW, LINU, LINV, LINW）of IGBT IPMs
- Protection Functions and Operation Sequences －Summary－
Product Information