2N5087
6
Motorola Small–Signal Transistors, FETs and Diodes Device Data
Figure 17. Thermal Response
t, TIME (ms)
1.0
0.01
r(t) TRANSIENT THERMAL RESIST ANCE
(NORMALIZED)
0.01
0.02
0.03
0.05
0.07
0.1
0.2
0.3
0.5
0.7
0.02 0.05 0.1 0.2 0.5 1.0 2.0 5.0 10 20 50 100 200 500 1.0 k 2.0 k 5.0 k 10 k 20 k
50 k
100 k
D = 0.5
0.2
0.1
0.05
0.02
0.01
SINGLE PULSE
DUTY CYCLE, D = t1/t
2
D CURVES APPLY FOR POWER
PULSE TRAIN SHOWN
READ TIME AT t1 (SEE AN–569)
Z
θ
JA(t)
= r(t) •R
θ
JA
T
J(pk)
– TA = P
(pk)
Z
θ
JA(t)
t
1
t
2
P
(pk)
FIGURE 19
Figure 18. Active–Region Safe Operating Area
TJ, JUNCTION TEMPERATURE (°C)
10
4
–40
I
C
, COLLECTOR CURRENT (nA)
Figure 19. Typical Collector Leakage Current
VCE, COLLECTOR–EMITTER VOL TAGE (VOLTS)
400
2.0
I
C
, COLLECTOR CURRENT (mA)
DESIGN NOTE: USE OF THERMAL RESPONSE DATA
A train of periodical power pulses can be represented by the model
as shown in Figure 19. Using the model and the device thermal
response the normalized effective transient thermal resistance of
Figure 17 was calculated for various duty cycles.
To find Z
θJA(t)
, multiply the value obtained from Figure 17 by the
steady state value R
θJA
.
Example:
The 2N5087 is dissipating 2.0 watts peak under the following
conditions:
t1 = 1.0 ms, t2 = 5.0 ms (D = 0.2)
Using Figure 17 at a pulse width of 1.0 ms and D = 0.2, the reading of
r(t) is 0.22.
The peak rise in junction temperature is therefore
∆T = r(t) x P
(pk)
x R
θJA
= 0.22 x 2.0 x 200 = 88°C.
For more information, see AN–569.
The safe operating area curves indicate IC–VCE limits of the
transistor that must be observed for reliable operation. Collector load
lines for specific circuits must fall below the limits indicated by the
applicable curve.
The data of Figure 18 is based upon T
J(pk)
= 150°C; TC or TA is
variable depending upon conditions. Pulse curves are valid for duty
cycles to 10% provided T
J(pk)
≤ 150°C. T
J(pk)
may be calculated from
the data in Figure 17. At high case or ambient temperatures, thermal
limitations will reduce the power than can be handled to values less
than the limitations imposed by second breakdown.
10
–2
10
–1
10
0
10
1
10
2
10
3
–20 0 + 20 +40 +60 +80 + 100 + 120 +140 + 160
VCC = 30 V
I
CEO
I
CBO
AND
I
CEX
@ V
BE(off)
= 3.0 V
TA = 25°C
CURRENT LIMIT
THERMAL LIMIT
SECOND BREAKDOWN LIMIT
1.0 ms
10 µs
TC = 25°C
1.0 s
dc
dc
4.0
6.0
10
20
40
60
100
200
4.0 6.0 8.0 10 20
40
TJ = 150°C
100 µs