NPN SILICON TRANSISTOR
SAFE OPERATING AREA INFORMATION
There are two limitations on the power handling ability of a transistor: average junction temperature and second
breakdown. Safe operating area curves indicate IC-VCE limits of the transistor that must be observed for reliable
operation; i.e., the transistor must not be subjected to greater dissipation than the curves indicate.
The data of Fig.5 is based on TC = 25°C; TJ(PK) is variable depending on power level. Second breakdown pulse
limits are valid for duty cycles to 10% but must be derated when TC≥25°C. Second breakdown limitations do not
derate the same as thermal limitations. Allowable current at the voltages shown on Fig.5.
TJ(PK) may be calculated from the data in Fig.4. At high case temperatures, thermal limitations will reduce the
power that can be handled to values less than the limitations imposed by second breakdown.
For inductive loads, high voltage and high current must be sustained simultaneously during turn-off, in most cases,
with the base to emitter junction reverse biased. Under these conditions the collector voltage must be held to a safe
level at or below a specific value of collector current. This can be accomplished by several means such as active
clamping, RC snubbing, load line shaping, etc. The safe level for these devices is specified as RBSOA( Reverse Bias
Safe Operating Area) and represents the voltage-current conditions during reverse biased turn-off. This rating is
verified under clamped conditions so that the device is never subjected to an avalanche mode. Fig.6 gives RBSOA
The Safe Operating Area of Fig.5 and 6 are specified ratings (for these devices under the test conditions shown.)
Fig.5 Active Region Safe Operating Area
Fig.6 Reverse Bias Safe Operating Area
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