250+ TOP MCQs on Basic BJT Amplifier Configuration and Answers

Electronic Devices and Circuits Multiple Choice Questions on “Basic BJT Amplifier Configuration”.

(Q1-Q.6) An amplifier is measured to have an internal resistance of 10 kΩ, voltage gain of 100V/V and output resistance of 100 Ω. Also, when a load resistance of 1 kΩ is connected between the output resistance if found to decrease to 8 kΩ. If the amplifier is fed with the signal source having an internal resistance of 2 kΩ, then
1. Find Gm.
A. 1 A/V
B. 10 A/V
C. 100 A/V
D. 1000 A/V

Answer: A
Clarification: Gm = (voltage gain in V/V) / (output resistance) or 100/100 A/V.

2. Find Av.
A. 9.09 V/V
B. 10 V/V
C. 90.9 V/V
D. 100 V/V

Answer: C
Clarification: Av = Avo X Rl/Ro+Rl or 100 X 1000/1000+100 or 90.9 V/V.

3. Find Gvo.
A. 53.3 V/V
B. 63.3 V/V
C. 73.3 V/V
D. 83.3 V/V

Answer: D
Clarification: Gvo = (Avo X input resistance) / (input resistance + signal resistance).

4. Find Gv.
A. 53.4 V/V
B. 72.7 V/V
C. 83.3 V/V
D. 90.9 V/V

Answer: B
Clarification: Gv = (Gvo X Av) / Avo or 83.3 X 90.9 / 100 V/V.

5. Find R out.
A. 146 Ω
B. 292 Ω
C. 584 Ω
D. 1168 Ω

Answer: A
Clarification: Rout = Rl (1 – Gvo/Gv). Put in the respective values and solve.

6. Find Ai.
A. 182 A/A
B. 364 A/A
C. 546 A/A
D. 728 A/A

Answer: D
Clarification: (Vo X R in) / (Vi X Rl) gives the required value of Ai.

(Q.7-Q.10) The circuit shown below is a small sine wave signal with average zero and transistor ß =

7. Find the value of R(E) to establish a dc emitter current of about 0.5 mA.
A. 28.57 kΩ
B. 57.04 kΩ
C. 114.08 kΩ
D. 228.16 kΩ

Answer: D
Clarification: V_c = 15 – R_c.I_c
5 = 15 – R_c * 0.99 * 0.5m
R_c = 20.2kΩ
= 20kΩ.

9. For R (L) = 10 kΩ and transistor Ro = 200 kΩ, determine the overall voltage gain.
A. -21 V/V
B. -42 V/V
C. -86 V/V
D. -123 V/V