# JFET Amplifier MCQ’s

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 V_{GS}=0

b) Transconductance decreases linearly with V_{GS}

c) Transconductance increases linearly with I_{DS}

d) Transconductance does not depend on V_{DS}

3. What are the small signal FET parameters?

a) g_{m} and r_{ds}

b) g_{m} and V_{gs}

c) V_{ds} and r_{ds}

d) g_{m}

4. Consider the circuit shown below.

Find the net output resistance given that g_{m} = 1mΩ^{-1} and r_{ds} = 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 g_{m} = 0.5mΩ^{-1} and r_{ds} = 0.2MΩ.

a) R_{I} = 27.27 kΩ, A_{V} = 5

b) R_{I} = 44 kΩ, A_{V} = 1

c) R_{I} = 27.27kΩ, A_{V} = 1

d) R_{I} = 60kΩ, A_{V} = 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 g_{m} = 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 r_{ds}=0.5MΩ and g_{m}=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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