BC856AWT1,BWT1 BC857AWT1,BWT1 BC858AWT1,BWT1,CWT1

5

Motorola Small–Signal Transistors, FETs and Diodes Device Data

Figure 13. Thermal Response

t, TIME (ms)

1.0

2.0

5.0

1.0

0.5

0.2

0.1

0.7

0.5

0.3

0.2

0.1

0.07

0.05

0.03

0.02

0.01

20

50

10

200

500

100

1.0 k

2.0 k

5.0 k

10 k

Figure 14. Active Region Safe Operating Area

VCE, COLLECTOR–EMITTER VOLTAGE (V)

–200

–1.0

TA = 25°C

D = 0.5

0.2

0.1

0.05

SINGLE PULSE

SINGLE PULSE

BONDING WIRE LIMIT

THERMAL LIMIT

SECOND BREAKDOWN LIMIT

3 ms

TJ = 25°C

Z

θJC(t) = r(t) RθJC

R

θJC = 83.3°C/W MAX

Z

θJA(t) = r(t) RθJA

R

θJA = 200°C/W MAX

D CURVES APPLY FOR POWER

PULSE TRAIN SHOWN

READ TIME AT t1

TJ(pk) – TC = P(pk) R

θJC(t)

t1

t2

P(pk)

DUTY CYCLE, D = t1/t2

–100

–50

–10

–5.0

–2.0

–5.0

–10

–30 –45 –65

–100

1 s

BC558

BC557

BC556

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 14 is based upon TJ(pk) = 150°C; TC or TA is

variable depending upon conditions. Pulse curves are valid for duty

cycles to 10% provided TJ(pk) ≤ 150°C. TJ(pk) may be calculated 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 secondary breakdown.