5
Motorola Bipolar Power Transistor Device Data
P
100
0
TC, CASE TEMPERATURE (
°
C)
0
40
200
80
60
40
20
MJ16018
MJW16018
80
120
160
Figure 15. Power Derating
SECOND BREAKDOWN
DERATING
THERMAL
DERATING
SAFE OPERATING AREA INFORMATION
FORWARD BIAS
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 13 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 der-
ate the same as thermal limitations. Allowable current at the
voltages shown on Figure 13 may be found at any case tem-
perature by using the appropriate curve on Figure 15.
TJ(pk) may be calculated from the data in Figure 16. At
high case temperatures, thermal limitations will reduce the
power that can be handled to values less than the limitations
imposed by second breakdown.
REVERSE BIAS
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 Reverse Bias Safe Operating Area
and represents the voltage current condition allowable dur-
ing reverse biased turnoff. This rating is verified under
clamped conditions so that the device is never subjected to
an avalanche mode. Figure 14 gives the RBSOA character-
istics.
t, TIME (ms)
1.0
0.7
0.5
0.01
0.01
0.2
0.1
0.07
0.05
0.02
r
1.0
2.0
5.0
10
20
50
100
200
500
R
θ
JC(t) = r(t) R
θ
JC
R
θ
JC = 1.0
°
C/W MAX
D CURVES APPLY FOR POWER
PULSE TRAIN SHOWN
READ TIME @ t1
TJ(pk) – TC = P(pk) R
θ
JC(t)
P(pk)
t1
t2
DUTY CYCLE, D = t1/t2
D = 0.5
0.2
0.01
SINGLE PULSE
0.1
0.1
0.5
0.2
1.0 k
Figure 16. Thermal Response
0.3
0.03
0.02
0.05
0.02
0.05