MJE18204 MJF18204

7

Motorola Bipolar Power Transistor Device Data

Figure 19. Forward Bias Power Derating

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

Figure 19 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 16 may be found at any case

temperature by using the appropriate curve on Figure 18.

TJ(pk) may be calculated from the data in Figures 21 and

22. 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 induc-

tive 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 17). This rating

is verified under clamped conditions so that the device is

never subjected to an avalanche mode.

TC, CASE TEMPERATURE (°C)

1.0

0.8

0.6

0.4

0.2

0

160

140

120

100

80

60

40

20

SECOND

BREAKDOWN

DERATING

THERMAL

DERATING

TYPICAL STATIC CHARACTERISTICS

Figure 20. Dynamic Saturation

Voltage Measurements

Figure 21. Inductive Switching Measurements

TYPICAL SWITCHING CHARACTERISTICS

(IB1 = IB2 FOR ALL CURVES)

TIME

10

4

0

8

2

0

6

8

6

2

4

9

7

5

3

1

1

3

5

7

VCE

0 V

IB

90% IB

1

µs

3

µs

dyn 1

µs

dyn 3

µs

IB

IC

Vclamp

tsi

tc

tfi

90% IC

10% IC

90% IB1

10% Vclamp

TIME