Transistor Bias Circuits - MCQs

Multiple Choice Questions Topic Outline

• MCQs in Transistor Bias Circuits
• MCQs in The DC Operating Point
• MCQs in Voltage-Divider Bias
• MCQs in Other Bias Methods
• MCQs in GreenTech Application 5: Wind Power

Begin and Good luck!

1. Voltage-divider bias has a relatively stable Q-point, as does

• A) base bias.
• B) collector-feedback bias.
• C) both of the above
• D) none of the above

2. Emitter bias requires

• A) only a positive supply voltage.
• B) only a negative supply voltage.
• C) no supply voltage.
• D) both positive and negative supply voltages.

3. Clipping is the result of

• A) the input signal being too large.
• B) the transistor being driven into saturation.
• C) the transistor being driven into cutoff.
• D) all of the above

4. Changes in β_DC result in changes in

• A) I_C.
• B) VC_E.
• C) the Q-point.
• D) all of the above

5. The input resistance at the base of a voltage-divider biased transistor can be neglected

• A) at all times.
• B) only if the base current is much smaller than the current through R2 (the lower bias resistor).
• C) at no time.
• D) only if the base current is much larger than the current through R₂ (the lower bias resistor).

6. What is the Q-point for a fixed-bias transistor with I_B = 75 µA, β_DC = 100, V_CC = 20 V, and R_C = 1.5 kΩ?

• A) V_C = 0 V
• B) V_C = 20 V
• C) V_C = 8.75 V
• D) V_C = 11.25 V

7. Ideally, for linear operation, a transistor should be biased so that the Q-point is

• A) near saturation.
• B) near cutoff.
• C) where I_C is maximum.
• D) halfway between cutoff and saturation.

8. Refer to Figure 5-1. The value of I_B is

Figure 5-1

• A) 53 µA.
• B) 50 µA.
• C) 50 mA.
• D) 53 mA.

9. Refer to Figure 5-1. The value of I_C is

• A) 10 µA.
• B) 10 mA.
• C) 5 mA.
• D) 50 mA.

10. Refer to Figure 5-1. The value of β_DC is

• A) 5.3.
• B) 53.
• C) 94.
• D) 100.

11. Refer to Figure 5-2. Determine I_C.

Figure 5-2

• A) 5 µA
• B) 5 mA
• C) 0 mA
• D) 10 mA

12. Refer to Figure 5-2. Assume that I_C ≈ I_E. Find V_E.

• A) 5 V
• B) 10 V
• C) 15 V
• D) 2.5 V

13. Refer to Figure 5-2. Assume I_C ≈ I_E. Determine the value of R_C that will allow V_CE to equal 10 V.

• A) 1 kΩ
• B) 1.5 kΩ
• C) 2 kΩ
• D) 2.5 kΩ

14. Refer to Figure 5-2. Calculate the current I₂.

• A) 32 mA
• B) 3.2 mA
• C) 168 µA
• D) 320 µA

15. Refer to Figure 5-3(a). The most probable cause of trouble, if any, from these voltage measurements would be

Figure 5-3

• A) the base-emitter junction is open.
• B) R_E is open.
• C) a short from collector to emitter.
• D) no problems.

16. Refer to Figure 5-3(b). The most probable cause of trouble, if any, from these voltage measurements is

• A) the base-emitter junction is open.
• B) RE is open.
• C) a short from collector to emitter.
• D) no problems.

17. Refer to Figure 5-3(c). The most probable cause of trouble, if any, from these voltage measurements is

• A) the base-emitter junction is open.
• B) R_E is open.
• C) a short from collector to emitter.
• D) no problems.

18. Refer to Figure 5-3(d). The most probable cause of trouble, if any, from these voltage measurements is

• A) the base-emitter junction is open.
• B) R_E is open.
• C) a short from collector to emitter.
• D) no problems.

19. The most stable biasing technique used is the

• A) voltage-divider bias.
• B) base bias.
• C) emitter bias.
• D) collector bias.

20. At saturation the value of V_CE is nearly _____, and I_C = _____.

• A) zero, zero
• B) V_CC, I_C(sat)
• C) zero, I_(sat)
• D) V_CC, zero

21. The linear (active) operating region of a transistor lies along the load line below _____ and above _____.

• A) cutoff, saturation
• B) saturation, cutoff

22. What is the most common bias circuit?

• A) base
• B) collector
• C) emitter
• D) voltage-divider

23. What is the dc input resistance at the base of a BJT?

• A) β_DCR_C
• B) βdc • (R_C || R_E)
• C) β_DC • r_e′
• D) β_DCR_E

24. Which transistor bias circuit provides good Q-point stability with a single-polarity supply voltage?

• A) base bias
• B) collector-feedback bias
• C) voltage-divider bias
• D) emitter bias

25. Which transistor bias circuit arrangement has poor stability because its Q-point varies widely with β_DC?

• A) base bias
• B) collector-feedback bias
• C) voltage-divider bias
• D) emitter bias

26. Which transistor bias circuit arrangement provides good Q-point stability, but requires both positive and negative supply voltages?

• A) base bias
• B) collector-feedback bias
• C) voltage-divider bias
• D) emitter bias

27. Which transistor bias circuit arrangement provides good stability using negative feedback from collector to base?

• A) base bias
• B) collector-feedback bias
• C) voltage-divider bias
• D) emitter bias

28.

FIGURE 5-4

Refer to Figure 5-4. In the voltage-divider biased npn transistor circuit, if R_C opens, the transistor is

• A) saturated.
• B) cutoff.
• C) nonconducting.

29. Refer to Figure 5-4. In the voltage-divider biased npn transistor circuit, if R₂ opens, the transistor is

• A) saturated.
• B) cutoff.
• C) nonconducting.

30. Refer to Figure 5-4. In the voltage-divider biased npn transistor circuit, if R₁ opens, the transistor is

• A) saturated.
• B) cutoff.
• C) nonconducting.

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