Performance of MOSFETs: Safe Operating Area(or Area of Safe Operation)

There are two modes of safe operating area (SOA).

(1) Forward Bias SOA (F.B. SOA): Usable area of current and voltage at ON status.
(2) Reverse Bias SOA (R.B. SOA): Usable area of current and voltage at turn-off operation.

Applied pulse width is very narrow because of use under switching operation.

Each mode can be defined as shown in Fig. 3-12(a).

Defining SOA in actual operation
Fig. 3-12(a) Defining SOA in actual operation
Example of MOSFET’s F.B.SOA
Fig. 3-12(b) Example of MOSFET’s F.B.SOA
  • As for the guarantee of avalanche, rated voltage / current operation (short time) at turn-off is generally guaranteed as for the MOSFET, but R. B. SOA has not been announced.
  • F.B.SOA consists of three restriction areas, rated current, rated voltage and thermal resistance areas, and secondary breakdown area.
  • The three restriction areas are limited by ratings of device or calculated from thermal resistance. But secondary breakdown area is obtained by measurement of the actual device.

Chapter III : Transistors

Types of Transistors
Bipolar Transistors (BJTs)
Bias Resistor Built-in Transistors (BRTs)
Junction Field-Effect Transistors (JFETs)
Metal-Oxide-Semiconductor Field-Effect Transistors (MOSFETs)
Differences between BJT and MOSFET
Structure and Operation of MOSFET
MOSFET Performance Improvement: Decision Factors of RDS(ON)
MOSFET Performance Improvement: Approach to Low RDS(ON)
MOSFET Performance Improvement: Super-Junction MOSFETs (SJ-MOS)
Summary of MOSFET Features by Structure
Performance of MOSFETs: Drain Current and Power Dissipation
Performance of MOSFETs: Avalanche Capability
Performance of MOSFETs: Characteristic of Capacitance
Insulated-Gate Bipolar Transistors (IGBTs)
Operation of Insulated-Gate Bipolar Transistors (IGBTs)
Performance Improvement of IGBTs: Evolution of Vertical Design
What are RC-IGBTs and IEGTs?
Application of IGBTs
Comparison of Forward Characteristics of IGBTs and MOSFETs
Comparison of Transistors by Structure
Datasheets of MOSFET: Maximum Ratings
Datasheets of MOSFET: Electrical Characteristics
Datasheets of MOSFET: Capacitance and Switching Characteristics
Datasheets of MOSFET: Body Diode

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