BUL44D2

9

Motorola Bipolar Power Transistor Device Data

SECOND BREAKDOWN

DERATING

THERMAL DERATING

Figure 23. Forward Bias Safe Operating Area

10

0.01

1000

10

VCE, COLLECTOR–EMITTER VOLTAGE (VOLTS)

Figure 24. Reverse Bias Safe Operating Area

2.5

1

0

900

200

VCE, COLLECTOR–EMITTER VOLTAGE (VOLTS)

100

1

0.1

DC

5 ms

1 ms

10

µs

1

µs

0.5

0 V

–1.5 V

– 5 V

TC ≤ 125°C

GAIN

≥ 4

LC = 500 µH

300

400

700

600

2

1.5

TYPICAL CHARACTERISTICS

500

800

Figure 25. Forward Bias Power Derating

1

0

160

100

20

TC, CASE TEMPERATURE (°C)

0.8

0.6

0.4

0.2

60

140

40

80

120

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 23 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 23 may be found at any case temperature by using

the appropriate curve on Figure 25.

TJ(pk) may be calculated from the data in Figure 26. 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 24). This rating is verified under clamped

conditions so that the device is never subjected to an

avalanche mode.