BUH51 Datasheet, PDF (8/10 Pages) Motorola, Inc – POWER TRANSISTOR 3 AMPERES 800 VOLTS 50 WATTS

BUH51
There are two limitations on the power handling ability of a
transistor: average junction temperature and second break-
down. 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 dissipa-
tion than the curves indicate. The data of Figure 22 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
Figure 22 may be found at any case temperature by using
the appropriate curve on Figure 21.
TJ(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.
100
10
1 ms
1
5 ms
DC
0.1
4
1 µs
3
10 µs
2
EXTENDED
SOA
1
GAIN ≥ 4
TC ≤ 125°C
LC = 500 µH
–5 V
0.01
10
100
1000
VCE, COLLECTOR–EMITTER VOLTAGE (VOLTS)
Figure 22. Forward Bias Safe Operating Area
0V
–1.5 V
0
200 300 400 500 600 700 800 900
VCE, COLLECTOR–EMITTER VOLTAGE (VOLTS)
Figure 23. Reverse Bias Safe Operating Area
TYPICAL THERMAL RESPONSE
1
0.5
0.2
0.1
0.1 _0.05
0.02
SINGLE PULSE
0.01
0.01
P(pk)
t1
t2
DUTY CYCLE, D = t1/t2
R_θJC(t) = r(t) R_θJC
R_θJC = 2.5°C/W MAX
D CURVES APPLY FOR POWER
PULSE TRAIN SHOWN
READ TIME AT t1
TJ(pk) – TC = P(pk) R_θJC(t)
0.1
1
10
100
1000
t, TIME (ms)
Figure 24. Typical Thermal Response (Z_θJC(t)) for BUH51
8
Motorola Bipolar Power Transistor Device Data