JFET Amplifier MCQ’s

Analog Electronic Circuits Electronics & Communication Engineering

This set of Analog Electronic Circuits Multiple Choice Questions & Answers (MCQs) focuses on “JFET Amplifier”.

1. Find the transconductance when applied gate to source voltage is -2V.


a) 10 Ω-1
b) 10mΩ-1
c) 40mΩ-1
d) 20mΩ-1

2. Choose the incorrect statement for JFET(s).
a) Maximum transconductance occurs at VGS=0
b) Transconductance decreases linearly with VGS
c) Transconductance increases linearly with IDS
d) Transconductance does not depend on VDS

3. What are the small signal FET parameters?
a) gm and rds
b) gm and Vgs
c) Vds and rds
d) gm

4. Consider the circuit shown below.


Find the net output resistance given that gm = 1mΩ-1 and rds = 0.1 MΩ.
a) 10 kΩ
b) 9.09 kΩ
c) 100 kΩ
d) 110 kΩ

5. Consider the amplifier below.


Find the input resistance and voltage gain of the circuit, given gm = 0.5mΩ-1 and rds = 0.2MΩ.
a) RI = 27.27 kΩ, AV = 5
b) RI = 44 kΩ, AV = 1
c) RI = 27.27kΩ, AV = 1
d) RI = 60kΩ, AV = 100

6. In a high-frequency model of a JFET, which of these capacitances is present?

A: Gate-to-source capacitance
B: Gate-to-drain capacitance
C: Drain-to-source capacitance

a) A and B
b) A and C
c) B and C
d) A, B and C

7. For an RC coupled common source JFET amplifier without bypass capacitor, find the voltage gain if gm = 1mΩ-1, source resistance is 2kΩ, drain resistance is 15kΩ and load is 10kΩ.
a) -2
b) -2.5
c) 5
d) 2

8. Which of these is incorrect for a common gate amplifier?
a) It is a current buffer
b) It has ∞ output resistance
c) Its input resistance is high
d) It is used as a high-frequency amplifier

9. Which of these is false for a CS amplifier without a bypass capacitor compared to a CS amplifier with a bypass capacitor?
a) Voltage gain magnitude decreases
b) Input resistance remains same
c) The output resistance decreases
d) The output is 180° out of phase with respect to the input applied

10. In a CS amplifier, given that rds=0.5MΩ and gm=5mΩ-1, the load is 10kΩ, source resistance is 44 kΩ. Calculate the internal amplification factor for the small signal model.
a) 2500
b) 8100
c) 9800
d) 7700

11. Which of these has an output which follows input?
a) CS amplifier with a bypass capacitor
b) CD amplifier
c) CG amplifier
d) CS amplifier without a bypass capacitor

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