# Circuit Models for Amplifier MCQ’s

This set of Electronic Devices & Circuits Multiple Choice Questions & Answers (MCQs) focuses on “Circuit Models for Amplifier”.

1. The ideal values for the input resistance (Ri) and the output resistance (Ro) of a transconductance amplifier are
a) Ri = 0 and Ro = 0
b) Ri = ∞ and R0 = ∞
c) Ri = 0 and R0 = ∞
d) Ri = ∞ and Ri = 0

2. An amplifier has a voltage gain of 40db. The value of AVO is
a) 10
b) 100
c) 20
d) 200

3. Buffer amplifier needs to have
a) Low input resistance and low output resistance
b) High Input resistance and high output resistance
c) Low input resistance and high output resistance
d) High input resistance and low output resistance

4. The output voltage of a voltage amplifier has been found to decrease by 20% when a load resistance of 1 kΩ is connected. What is the value of the amplifier output resistance?
a) 50Ω
b) 200Ω
c) 250Ω
d) 350Ω

5. The signal to be amplified is current signal and the output desired is a voltage signal. Which of the following amplifier can perform this task?
a) Voltage amplifier
b) Current amplifier
c) Transconductance amplifier
d) Transresistance amplifier

6. A transconductance amplifier with Ri = 2 kΩ, Gm = 40 mA/V, and Ro = 20 kΩ is fed with a voltage source having a source resistance of 2 kΩ and is loaded with a 1-kΩ resistance. Find the voltage gain realized.
a) 18.05 V/V
b) 19.05 V/V
c) 20.05 V/V
d) 21.05V/V

7. Which of the following is a transresistance amplifier?

a)

b)

c)

d)

8. You are given two amplifiers, A and B, to connect in cascade between a 10-mV, 100-kΩ source (S) and a 100-Ω load (L). The amplifiers have voltage gain, input resistance, and output resistance as follows: for A, 100 V/V, 10 kΩ, 10 kΩ, respectively; for B, 1 V/V, 100 kΩ, 100 Ω, respectively. Your problem is to decide how the amplifiers should be connected so that the voltage gain is maximum.
a) SABL
b) SBAL
c) Both have the same voltage gain
d) None as neither combination is able to amplify the input signal

9. The ratio of the short circuit current gain of a current amplifier (Ai) to the open circuit voltage gain of a voltage amplifier (AV), given that both amplifiers have the same value of the input resistance (Ri) and output resistance (R0), is
a) Ri
b) Ro
c) Ri / R0
d) Ro / Ri

10. The ratio of the open circuit voltage of a voltage amplifier (AV) to the short circuit transconductance of a (Gm) of a transconductance amplifier, given that both have the same value of the internal resistance (Ri) and the output resistance (R0), is
a) Ri
b) R0
c) 1/Ri
d) 1/R0

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