safe operating area
英[seif ˈɔpəˌreɪtɪŋ ˈɛəriə]美[sef ˈɑpəˌretɪŋ ˈɛriə]
For power semiconductor devices (such as BJT, MOSFET, thyristor or IGBT), the safe operating area (SOA) is defined as the voltage and current conditions over which the device can be expected to operate without self-damage. Tim Williams ,The circuit designer's companion 2nd ed.