LESHAN RADIO COMPANY, LTD.
BC856AWT1, BWT1 BC857AWT1, BWT1, BC858AWT1, BWT1, CWT1
r( t), TRANSIENT THERMAL
RESISTANCE (NORMALIZED)
1.0
0.7
0.5
0.3
0.2
D=0.5
0.2
SINGLE PULSE
0.1
0.1
0.07
0.05
0.03
0.02
0.01
0.1
0.05
SINGLE PULSE
P
(pk)
t
1
t
2
DUTY CYCLE, D = t
1
/t
2
Z
θJC
(t) = r(t) R
θJC
R
θJC
= 83.3°C/W MAX
Z
θJA
(t) = r(t) R
θJA
R
θJA
= 200°C/W MAX
D CURVES APPLY FOR POWER
PULSE TRAIN SHOWN
READ TIME AT t
1
T
J(pk)
– T
C
= P
(pk)
R
θJC
(t)
0.2
0.5
1.0
2.0
5.0
10
20
t, TIME (ms)
50
100
200
500
1.0k 2.0k
5.0k
10k
Figure 13. Thermal Response
–200
1s
I
C
, COLLECTOR CURRENT (mA)
3 ms
–100
–50
T
A
= 25°C
T
J
= 25°C
The safe operating area curves indicate I
C
–V
CE
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 14 is based upon T
J(pk)
= 150°C; T
C
or T
A
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 calcu-
lated from the data in Figure 13. At high case or ambient
temperatures, thermal limitations will reduce the power that can
be handled to values less than the limitations imposed by the sec-
ondary breakdown.
–10
–5.0
BC558
BC557
BC556
BONDING WIRE LIMIT
THERMAL LIMIT
SECOND BREAKDOWN LIMIT
–2.0
–1.0
–0.5
–10
–30 –45 –65 –100
V
CE
, COLLECTOR–EMITTER VOLTAGE (V)
Figure 14. Active Region Safe Operating Area
K5–5/5
LRC [ LESHAN RADIO COMPANY ]
