1. For the fixed-bias configuration of Fig. 4.118 , determine:

a. IBQ.

b. ICQ.

c. VCEQ.

d. V C .

e. V B .

f. V E .

ICQ

510 k

1.8 k

=120

FIG. 4.118

Problems 1, 4, 6, 7, 14, 65, 69,

71, and 75.

VC

IB = 40 A

IC

= 6 V

12 V

+

VCE = 80

RB

RC

FIG. 4.119

Problem 2.

FIG. 4.120

Problem 3.

2. Given the information appearing in Fig. 4.119 , determine:

a. I C .

b. R C .

c. R B .

d. V CE .

3. Given the information appearing in Fig. 4.120 , determine:

a. I C .

b. V CC .

c. b.

d. R B .

4. Find the saturation current (ICsat) for the fixed-bias configuration of Fig. 4.118 . LAST H1 HEAD PROBLEMS 239

*5. Given the BJT transistor characteristics of Fig. 4.121 :

a. Draw a load line on the characteristics determined by E = 21 V and RC = 3 k for a

fixed-bias configuration.

b. Choose an operating point midway between cutoff and saturation. Determine the value of

R B to establish the resulting operating point.

c. What are the resulting values of ICQ and VCEQ?

d. What is the value of b at the operating point?

e. What is the value of a defined by the operating point?

f. What is the saturation current (ICsat) for the design?

g. Sketch the resulting fixed-bias configuration.

h. What is the dc power dissipated by the device at the operating point?

i. What is the power supplied by V CC ?

j. Determine the power dissipated by the resistive elements by taking the difference between

the results of parts (h) and (i).

0

10

9

8

7

6

5

4

3

2

1

5 10 15 20 25 30 VCE (V)

IC (mA)

110 A

100 A

90 A

80 A

70 A

60 A

50 A

40 A

30 A

20 A

10 A

IB = 0 A

FIG. 4.121

Problems 5, 6, 9, 13, 24, 44, and 57.

6. a. Ignoring the provided value of b(120) draw the load line for the network of Fig. 4.118 on the

characteristics of Fig. 4.121 .

b. Find the Q -point and the resulting ICQ and VCEQ.

c. What is the beta value at this Q -point?

7. If the base resistor of Fig. 4.118 is increased to 910 k, find the new Q -point and resulting

values of ICQ and VCEQ.

4.4 Emitter-Bias Configuration

8. For the emitter-stabilized bias circuit of Fig. 4.122 , determine:

a. IBQ.

b. ICQ.

c. VCEQ.

d. V C .

e. V B .

f. V E .

SEMICONDUCTOR

DIODES

240 DC BIASINGBJTs

9. a. Draw the load line for the network of Fig. 4.122 on the characteristics of Fig. 4.121 using b

from problem 8 to find IBQ.

b. Find the Q -point and resulting values ICQ and VCEQ.

c. Find the value of b at the Q -point.

d. How does the value of part (c) compare with b 125 in problem 8?

e. Why are the results for problem 9 different from those of problem 8?

10. Given the information provided in Fig. 4.123 , determine:

a. R C .

b. R E .

c. R B .

d. V CE .

e. V B .

11. Given the information provided in Fig. 4.124 , determine:

a. b.

b. V CC .

c. R B .

270 k

470

2.2 k

=125

FIG. 4.122

Problems 8, 9, 12, 14, 66, 69, 72, and 76.

FIG. 4.123

Problem 10.

FIG. 4.124

Problem 11.

12. Determine the saturation current (ICsat) for the network of Fig. 4.122 .

*13. Using the characteristics of Fig. 4.121 , determine the following for an emitter-bias configuration if a Q -point is defined at ICQ = 4 mA and VCEQ = 10 V.

a. R C if VCC = 24 V and RE = 1.2 k.

b. b at the operating point.

c. R B .

d. Power dissipated by the transistor.

e. Power dissipated by the resistor R C .

*14. a. Determine I C and V CE for the network of Fig. 4.118 . LAST H1 HEAD PROBLEMS 241

b. Change b to 180 and determine the new value of I C and V CE for the network of Fig. 4.118 .

c. Determine the magnitude of the percentage change in I C and V CE using the following

equations:

%IC = `

IC(part b) - IC(part a)

IC(part a)

` * 100%, %VCE = `

VCE(part b) - VCE(part a)

VCE(part a)

` * 100%

d. Determine I C and V CE for the network of Fig. 4.122 .

e. Change b to 187.5 and determine the new value of I C and V CE for the network of Fig. 4.122 .

f. Determine the magnitude of the percentage change in I C and V CE using the following

equations:

%IC = `

IC(part c) - IC(part d)

IC(part d)

` * 100%, %VCE = `

VCE(part c) - VCE(part d)

VCE(part d)

` * 100%

g. In each of the above, the magnitude of b was increased 50%. Compare the percentage

change in I C and V CE for each configuration, and comment on which seems to be less sensitive to changes in b.

4.5 Voltage-Divider Bias Configuration

15. For the voltage-divider bias configuration of Fig. 4.125 , determine:

a. IBQ.

b. ICQ.

c. VCEQ.

d. V C .

e. V E .

f. V B .

16. a. Repeat problem 15 for b 140 using the general approach (not the approximate).

b. What levels are affected the most? Why?

17. Given the information provided in Fig. 4.126 , determine:

a. I C .

b. V E .

c. V B .

d. R1 .

FIG. 4.125

Problems 15, 16, 20, 23, 25, 67,

69, 70, 73, and 77.

FIG. 4.126

Problems 17 and 19.

18. Given the information appearing in Fig. 4.127 , determine:

a. I C .

b. V E .

c. V CC .

d. V CE .

e. V B .

f. R1 .

SEMICONDUCTOR

DIODES

242 DC BIASINGBJTs

19. Determine the saturation current (ICsat) for the network of Fig. 4.125 .

20. a. Repeat problem 16 with b 140 using the approximate approach and compare results.

b. Is the approximate approach valid?

*21. Determine the following for the voltage-divider configuration of Fig. 4.128 using the approximate approach if the condition established by Eq. (4.33) is satisfied.

a. I C .

b. V CE .

c. I B .

d. V E .

e. V B .

VE

FIG. 4.127

Problem 18.

FIG. 4.128

Problems 21, 22, and 26.

*22. Repeat Problem 21 using the exact (Thvenin) approach and compare solutions. Based on the

results, is the approximate approach a valid analysis technique if Eq. (4.33) is satisfied?

23. a. Determine ICQ, VCEQ, and IBQ for the network of Problem 15 ( Fig. 4.125 ) using the approximate approach even though the condition established by Eq. (4.33) is not satisfied.

b. Determine ICQ, VCEQ, and IBQ using the exact approach.

c. Compare solutions and comment on whether the difference is sufficiently large to require

standing by Eq. (4.33) when determining which approach to employ.

*24. a. Using the characteristics of Fig. 4.121 , determine R C and R E for a voltage-divider network

having a Q -point of ICQ = 5 mA and VCEQ = 8 V. Use VCC = 24 V and RC = 3RE.

b. Find V E .

c. Determine V B .

d. Find R2 if R1 = 24 k assuming that bRE 7 10R2.

e. Calculate b at the Q -point.

f. Test Eq. (4.33), and note whether the assumption of part (d) is correct.

*25. a. Determine I C and V CE for the network of Fig. 4.125 . LAST H1 HEAD PROBLEMS 243

b. Change b to 120 (50% increase), and determine the new values of I C and V CE for the network of Fig. 4.125 .

c. Determine the magnitude of the percentage change in I C and V CE using the following

equations:

%IC = `

IC(part b) - IC(part a)

IC(part a)

` * 100%, %VCE = `

VCE(part b) - VCE(part a)

VCE(part a)

` * 100%

d. Compare the solution to part (c) with the solutions obtained for parts (c) and (f) of Problem 14.

e. Based on the results of part (d), which configuration is least sensitive to variations in b?

*26. a. Repeat parts (a) through (e) of Problem 25 for the network of Fig. 4.128 . Change b to 180

in part (b).

b. What general conclusions can be made about networks in which the condition bRE 7 10R2

is satisfied and the quantities I C and V CE are to be determined in response to a change in b?