MOSFET in Amplifier Design MCQ’s

This set of Electronic Devices & Circuits Multiple Choice Questions & Answers (MCQs) focuses on “MOSFET in Amplifier Design”.

(Q.1 & Q.2) Various measurements are made on an NMOS amplifier for which the drain resistor RD is 20 kΩ. First, DC measurements show the voltage across the drain resistor, VRD, to be 2 V and the gate-to-source bias voltage to be 1.2 V. Then, ac measurements with small signals show the voltage gain to be −10 V/V.

1. If the process transconductance parameter is 50μA/V2, what is the MOSFET’s W/L?
a) 25
b) 50
c) 75
d) 100

2. What is the value of Vt for this transistor?
a) 0.7V
b) 0.8V
c) 0.9V
d) 1.0V

(Q.3-Q.5) Consider the amplifier below for the case VDD = 5 V, RD = 24 kΩ, (W/L) = 1 mA/V2, and Vt = 1 V.


3. For amplifier biased to operate with an overdrive voltage of 0.5V, and disregarding the distortion caused by the MOSFET’s square-law characteristic, what is the largest amplitude of a sine-wave voltage signal that can be applied at the input while the transistor remains in saturation?
a) 1.61 V
b) 1.5 V
c) 0.11 V
d) 3.11 V

4. If the amplifier is biased to operate with an overdrive voltage VOV of 0.5 V, find the incremental gain at the bias point.
a) -3 V/V
b) -6 V/V
c) -9 V/V
d) -12 V/V

5. For the input signal of 1.5V what is the value of the gain value obtained?
a) -12.24 V/V
b) -12.44 V/V
c) -12.64 V/V
d) -12.84 V/V

6. Bias point is also referred by the name
a) DC Operating Point
b) Quiescent Point
c) None of the mentioned
d) All of the mentioned

7. Which of the following is the fastest switching device?
b) Triode
d) BJT

(Q.8 –Q.10) Consider the amplifier circuit shown below. The transistor is specified to have Vt = 0.4 V, kn = 0.4 mA/V2, W/L = 10 and λ = 0. Also, let VDD = 1.8V, RD = 17.5kΩ, VGS = 0.6V and vgs = 0V.


8. Find ID.
a) 0.08 mA
b) 0.16 mA
c) 0.4 mA
d) 0.8 mA

9. Find Av.
a) -12 V/V
b) -14 V/V
c) -16 V/V
d) -18 V/V

10. Find VDS.
a) 0.1V
b) 0.2 V
c) 0.4 V
d) 0.8 V

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