BUH51
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8
TYPICAL THERMAL RESPONSE
Figure 21. Forward Bias Power Derating
1
0
16010020
T
C
, CASE TEMPERATURE (°C)
0.8
POWER DERATING FACTOR
0.6
0.4
0.2
60 140
SECOND BREAKDOWN
DERATING
40 80 120
THERMAL DERATING
There are two limitations on the power handling ability of
a transistor: average junction temperature and second
breakdown. Safe operating area curves indicate I
C
−V
CE
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 Figure 22 is
based on T
C
= 25°C; T
J(pk)
is variable depending on power
level. Second breakdown pulse limits are valid for duty
cycles to 10% but must be derated when T
C
> 25°C. Second
breakdown limitations do not derate the same as thermal
limitations. Allowable current at the voltages shown on
Figure 22 may be found at any case temperature by using the
appropriate curve on Figure 21.
T
J(pk)
may be calculated from the data in Figure 24. At any
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 current must be sustained simultaneously during
turn−off with the base to emitter junction reverse biased. The
safe level is specified as a reverse biased safe operating area
(Figure 23). This rating is verified under clamped conditions
so that the device is never subjected to an avalanche mode.
Figure 22. Forward Bias Safe Operating Area
100
0.01
100010
V
CE
, COLLECTOR−EMITTER VOLTAGE (VOLTS)
Figure 23. Reverse Bias Safe Operating Area
4
2
0
900200
V
CE
, COLLECTOR−EMITTER VOLTAGE (VOLTS)
100 500
1
0.1
I
C
, COLLECTOR CURRENT (AMPS)
I
C
, COLLECTOR CURRENT (AMPS)
DC
5 ms
1 ms 10 μs
1 μs
3
1
GAIN ≥ 4
−1.5 V
−5 V
T
C
≤ 125°C
L
C
= 500 μH
10
300 400 700600 800
EXTENDED
SOA
0 V
