Electronic Devices and Circuits Questions and Answers – Discrete-Circuit MOS Amplifiers

This set of Advanced Electronic Devices and Circuits Questions and Answers focuses on “Discrete-Circuit MOS Amplifiers”.

1. Calculate the overall voltage gain Gv of a common source amplifier for which gm = 2mA/V, RD = 10 kΩ, R0 = 10 kΩ and RG = 10 MΩ. The amplifier is fed from a signal source of Thevenin resistance of 0.5MΩ and the amplifier is coupled with a load of 10 kΩ.
a) -11.2 V/V
b) -22.4 V/V
c) -33.6 V/V
d) -44.8 V/V
View Answer

Answer: a
Explanation:
Overall voltage gain Gv of source amplifier for which gm = 2mA/V, R0 = 10 kΩ is -11.2 V/V

2. The MOSFET circuit below has Vt = 1V, knW/L = 0.8 mA/V2 and VA = 40V. Find the value of RG so that iD = 0.1 mA, the largest possible value of RD is used while the maximum signal swing at the drain is of 1V and the input resistance at the gate is 10 MΩ.
Find the value of RG so that iD = 0.1 mA, the largest possible value of RD is used
a) 1 MΩ
b) 10 MΩ
c) 0.1 MΩ
d) 0.01 MΩ
View Answer

Answer: b
Explanation:
The value of RG so that iD = 0.1 mA, the largest possible value of RD is used is 10 MΩ

3. The MOSFET circuit below has Vt = 1V, knW/L = 0.8 mA/V2 and VA = 40V. Find the value of gm at the bias point.
Find the value of RG so that iD = 0.1 mA, the largest possible value of RD is used
a) 0.1 mA/V
b) 0.2 mA/V
c) .0.3 mA/V
d) 0.4 mA/V
View Answer

Answer: d
Explanation:
Find the value of gm at the bias point for MOSFET circuit below has Vt = 1V
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4. The MOSFET circuit below has Vt = 1V, knW/L = 0.8 mA/V2 and VA = 40V. If terminal Z is grounded, X is connected to a signal source having a resistance of 1 MΩ and terminal Y is connected to a load resistance of 40 kΩ, find the voltage gain from the signal source to the load.
Find the value of RG so that iD = 0.1 mA, the largest possible value of RD is used
a) 3.25 v/V
b) 6.5 V/V
c) 9.75 V/V
d) 13 V/V
View Answer

Answer: b
Explanation:
The voltage gain from signal source to load is 6.5 V/V for MOSFET circuit has Vt = 1V

5. The MOSFET circuit below has Vt = 1V, knW/L = 0.8 mA/V2 and VA = 40V. If terminal Y is grounded find the voltage gain from X to Z with Z open-circuit.
Find the value of RG so that iD = 0.1 mA, the largest possible value of RD is used
a) 0.33 V/V
b) 0.66 V/V
c) 0.99 V/V
d) None of the mentioned
View Answer

Answer: c
Explanation:
Voltage gain from X to Z with Z open-circuit is 0.99 V/V for MOSFET circuit has Vt = 1V

6. The MOSFET circuit below has Vt = 1V, knW/L = 0.8 mA/V2 and VA = 40V. If terminal X is grounded and terminal Z is connected to a current source delivering a current of 10 µA and having a resistance of 100 kΩ, find the voltage signal that can be measured at Y neglecting the effect of V0.
Find the value of RG so that iD = 0.1 mA, the largest possible value of RD is used
a) 0.34V
b) 0.68 V
c) 3.4 V
d) 6.8 V
View Answer

Answer: a
Explanation:
The voltage signal that can be measured at Y neglecting the effect of V0 is 0.34V

7. The NMOS transistor in source follower circuit shown has gm = 5mA/V and a large r0. Find the output resistance.
Find output resistance if NMOS transistor in source follower circuit has gm = 5mA/V
a) 0.1 kΩ
b) 0.2 kΩ
c) 0.3 kΩ
d) 0.4 kΩ
View Answer

Answer: b
Explanation:
Output resistance if NMOS transistor in source follower circuit has gm = 5mA/V is 0.2 kΩ
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8. The NMOS transistor in source follower circuit shown has gm = 5mA/V and a large r0. Find the open-Circuit voltage gain.
Find open-Circuit voltage gain if NMOS transistor in follower circuit has gm = 5mA/V
a) 1 V/V
b) 2 V/V
c) 3 V/V
d) 4 V/V
View Answer

Answer: a
Explanation:
Open-Circuit voltage gain is 1 V/V if NMOS transistor in follower circuit has gm = 5mA/V

Open-Circuit voltage gain is 1 V/V if NMOS transistor in follower circuit has gm = 5mA/V

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9. The NMOS transistor in the common gate amplifier as shown in the circuit below has gm = 5 mA/V. Find the input resistance and the voltage gain.
Find input resistance & the voltage gain if gate amplifier in circuit has gm = 5 mA/V
a) Input resistance: 0.1 kΩ and Voltage gain: 3.05 V/V
b) Input resistance: 0.1 kΩ and Voltage gain: 3.05 V/V
c) Input resistance: 0.2 kΩ and Voltage gain: 3.05 V/V
d) Input resistance: 0.2 kΩ and Voltage gain: 7.1 V/V
View Answer

Answer: d
Explanation:
The input resistance & the voltage gain is 0.2 kΩ & 7.1 V/V in given diagram

10. If the output of the source follower in (I) is connected to the input of the common gate amplifier of (II). Determine the overall voltage gain (V0 /Vi).
Find overall voltage gain if output of follower is connected to input of gate amplifier
a) 1.55 V/V
b) 3.55 V/V
c) 5.55 V/V
d) 7.55 V/V
View Answer

Answer: b
Explanation:
The overall voltage gain (V0 /Vi) is 3.55 V/V if output is connected to input

Sanfoundry Global Education & Learning Series – Electronic Devices and Circuits.

To practice Advanced questions and answers on all areas of Electronic Devices and Circuits, here is complete set of 1000+ Multiple Choice Questions and Answers.

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Manish Bhojasia, a technology veteran with 20+ years @ Cisco & Wipro, is Founder and CTO at Sanfoundry. He lives in Bangalore, and focuses on development of Linux Kernel, SAN Technologies, Advanced C, Data Structures & Alogrithms. Stay connected with him at LinkedIn.

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