250+ TOP MCQs on BJT Configuration and Answers

Analog Circuits Multiple Choice Questions on “BJT Configuration”.

1. For a BJT, for common base configuration the input characteristics are represented by a plot between which of the following parameters?
A. V_BE and I_E
B. V_BE and I_B
C. V_CE and I_C
D. V_CC and I_C

Answer: A
Clarification: The input signal is applied between the base and the emitter terminals. Input current flowing is the base current and hence characteristics are represented by a plot between V_BE and I_B.

2. For a BJT, for common base configuration the output characteristics are represented by a plot between which of the following parameters?
A. V_BE and I_B
B. V_CE and I_C
C. V_CB and I_C
D. V_CE and I_B

Answer: C
Clarification: The input signal is applied between the collector and the emitter terminals. Input current flowing is the collector current and hence characteristics are represented by a plot between V_CE and I_C.

3. In a BJT, if the collector-base junction is reverse-biased and the base-emitter junction is forward-biased, which region is the BJT operating in?
A. Saturation region
B. Active region
C. Cutoff region
D. Reverse active region

Answer: b
Clarification: If the collector-base junction is reverse-biased and the base-emitter junction is forward-biased, then the BJT functions in the active region of the output characteristics.

4. In a BJT, if the collector-base junction is forward-biased and the base-emitter junction is forward-biased, which region is the BJT operating in?
A. Saturation region
B. Active region
C. Cutoff region
D. Reverse active region

Answer: A
Clarification: If the collector-base junction and the base-emitter junction are both forward-biased, then the BJT functions in the saturation region of the output characteristics.

5. In a BJT, if the collector-base junction and the base-emitter junction are both reverse-biased, which region is the BJT operating in?
A. Saturation region
B. Active region
C. Cutoff region
D. Reverse active region

Answer: C
Clarification: If the collector-base junction and the base-emitter junction are both reverse-biased, then the BJT functions in the cutoff region of the output characteristics.

6. From the given characteristics, what is the approximate value of I_C at I_B=30 uA and V_CE=10 V?

A. 3 mA
B. 3.4 mA
C. 0 mA
D. 2 mA

Answer: B
Clarification: At the intersection of I_B=30 uA and V_CE=10 V, I_C=3.4 mA.

7. From the given characteristics, what is the approximate value of I_C at V_BE=0.7 V and V_CE=15 V?

A. 3.4 mA
B. 0 mA
C. 2.5 mA
D. 10 mA

Answer: C
Clarification: From the characteristics, the value of I_B at V_BE=0.7V is 20uA. Now, from I_B=20 uA, we get I_C = 2.5 mA.

8. Which of the following correctly determines the relation between α and β?
A. β=α/(1-α)
B. α=β/(1-α)
C. β=α/(1-β)
D. β=α*(1-β)

Answer: a
Clarification: α and β are related as β=α/(1-α).
In a BJT, β = I_C/I_B. and α = I_C/I_E
β = αI_E/I_B = (1+β)α
β = α + αβ
β = α/1-α.

9. The value of I_C is precisely zero when the value of I_E is zero.
A. True
B. False

Answer: B
Clarification: When the value of I_E is zero, then the value of I_C is equal to I_CBO which is in the order of microamperes but not zero.

10. For common emitter configuration, which of the following is the correct relation?
A. I_C < I_E
B. I_C = βI_B
C. I_C = αI_E
D. I_C = I_E

Answer: D
Clarification: All the relations hold true i.e. I_C = βI_B and I_C = αI_E. As α<1, hence I_C < I_E.