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What is the difference between MOSFETs and IGBTs?

There are three major types of transistors: bipolar transistors, MOSFETs, and IGBTs. The following table compares the performance and characteristics of these transistors. Bipolar transistors are now hardly ever used for power electronics and switching applications because of the need for drive and protection circuits and slow switching speed. Instead, MOSFETs and IGBTs are selectively used according to the required characteristics. The figure given alongside shows the on-state voltage characteristics of a 30-A IGBT and a 31-A super-junction MOSFET (SJMOS).

In the low-current region, the MOSFET exhibits a lower on-state voltage than the IGBT. However, in the high-current region, the IGBT exhibits lower on-state voltage than the MOSFET, particularly at high temperature. IGBTs are commonly used at a switching frequency lower than 20 kHz because they exhibit higher switching loss than unipolar MOSFETs.

 

Forward characteristic comparison : IGBT vs. MOSFET

Forward characteristic comparison : IGBT vs. MOSFET

Comparison of the performance of different types of transistors

Type Bipolar transistors MOSFETs IGBTs
Gate (base) drive

Current drive

(Low input impedance)

Voltage drive

(High input impedance)

Voltage drive

(High input impedance)

Gate (base) drive circuit Complicated for switching applications Relatively simple Relatively simple
On-state voltage characteristics Low VCE(sat)

On-resistance x drain current

Without built-in voltage(*1)

Low VCE(sat)

With built-in voltage(*1)

Switching time

Slow

(Carrier accumulation effect)

Ultra-high speed

(Unipolar device)

High speed

(Faster than bipolar transistors and slower than MOSFETs)

Parasitic diode Not present Present (body diode) Present only in RC-IGBTs

(*1)  The built-in voltage is a threshold voltage inherent to a device. Here, the built-in voltage refers to the forward threshold voltage.

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