0195136047.pdf

PROBLEMS 387

+−vπ

∆vBE = 0.05 V ∆vL RL = 10 kΩ

0.03 vπ

ro

C

B

E

rπ

+

−

+

−

Figure P7.3.7

E

−2.0

−1.5

−1.0

−0.5

0

(b)

Load line

− 5 − 10 − 15 − 20

VCC

iB = 0

iB = −40 mA

−35 mA

−30 mA

−25 mA

−20 mA

= −15 mA

−10 mA

−5 mA

Q IBQ

vC, V

iC

, A

(a)

B

C

+

−

+

−

ib IBB VCC

RL

vC

iC

iB

Figure P7.3.8

(b) ForVCC=18 V, if the operatingQpoint is

at a collector voltage of 10 V and a collector

current of 16 mA, determine theRCandRB

needed to establish the operating point.

7.3.10The two-transistor combination known as Dar-
lington pair or Darlington compound transistor is
often used as a single three-terminal device, as

shown in Figure P7.3.10. Assuming the transistors

to be identical, neglectingICBOof each BJT, find

αCandβCof the combination.

*7.3.11The circuit of Figure P7.3.11 uses apnpBJT

whose characteristics are shown in Figure 7.3.6.

The parameter values areRC = 30 , RB =

6k, VCC=60 V, andVBE=− 0 .7V.