Electronic Devices and Circuits Questions and Answers – Biasing in MOS Amplifier Circuit

This set of Electronic Devices and Circuits Problems focuses on “Biasing in MOS Amplifier Circuit”.

1. A discrete MOSFET common source amplifier has Rin = 2 MΩ, gmm = 4mA/V, ro = 100 kΩ, RD = 10 kΩ, Cgs = 2pF and Cgd = 0.5pF. The amplifier is fed from a voltage source with an internal resistance of 500 kΩ and Is connected to the a load of 10 kΩ. The value of the overall mixed gain AM is?
a) -15.2 V/V
b) -16.2 V/V
c) -17.2 V/V
d) -18.2 V/V
View Answer

Answer: a
Explanation:
The value of overall mixed gain AM is -15.2 V/V for MOSFET source amplifier has Rin = 2 MΩ

2. A discrete MOSFET common source amplifier has Rin = 2 MΩ, gmm = 4mA/V, ro = 100 kΩ, RD = 10 kΩ, Cgs = 2pF and Cgd = 0.5pF. The amplifier is fed from a voltage source with an internal resistance of 500 kΩ and Is connected to the a load of 10 kΩ. The upper 3-db frequency fH is?
a) 11.1 kHz
b) 22.1 kHz
c) 33.1 kHz
d) 44.1 kHz
View Answer

Answer: c
Explanation:
The upper 3-db frequency fH is 33.1 kHz for MOSFET source amplifier has Rin = 2 MΩ

3. The amplifier in the figure shown below is biased to operate at ID = 1mA and gm = 1mA/V. Find the midband gain.
Find the midband gain in the figure biased to operate at ID = 1mA & gm = 1mA/V
a) 0.43 V/V
b) 1.43 V/V
c) 2.43 V/V
d) 3.43 V/V
View Answer

Answer: b
Explanation:
Midband gain biased to operate at ID = 1mA & gm = 1mA/V is 1.43 V/V
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4. The amplifier in the figure shown below is biased to operate at ID = 1mA and gm = 1mA/V. Find the value of CS that places FL at 10Hz.
Find the midband gain in the figure biased to operate at ID = 1mA & gm = 1mA/V
a) 6.57 µF
b) 12.57 µF
c) 18.57 µF
d) 24.57 µF
View Answer

Answer: c
Explanation:
The value of CS that places FL at 10Hz is 18.57 µF to operate at ID = 1mA & gm = 1mA/V

5. In the NMOS transistor of the circuit shown below is biased to have gm = 1mA/V and r0 = 100 kΩ. Find AM.
Find AM in NMOS transistor of circuit is biased to have gm = 1mA/V & r0 = 100 kΩ
a) 1.02 V/V
b) 2.04 V/V
c) 3.06 V/V
d) 4.08 V/V
View Answer

Answer: c
Explanation:
Midband gain biased to operate at ID = 1mA & gm = 1mA/V is 1.43 V/V
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6. In the NMOS transistor of the circuit shown below is biased to have gm = 1mA/V and r0 = 100 kΩ. Find fH if Cgs = 1 pF and Cgd = 0.2 pF.
Find AM in NMOS transistor of circuit is biased to have gm = 1mA/V & r0 = 100 kΩ
a) 875 kHz
b) 875 kHz
c) 875 kHz
d) 875 kHz
View Answer

Answer: c
Explanation:
Find fH if Cgs = 1 pF & Cgd = 0.2 pF if NMOS transistor is biased to have gm = 1mA/V

7. For a particular depletion mode NMOS device, Vt = -2V, kn W/L = 200 µA/V2 and λ = 0.02V-1. For VDS = 2V. What is the drain current that flows
a) 104 µA
b) 208 µA
c) 312µA
d) 416 µA
View Answer

Answer: d
Explanation:
The drain current that flows 416 µA for depletion mode NMOS device, Vt = -2V, kn
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8. For a particular depletion mode NMOS device, Vt = -2V, kn W/L = 200 µA/V2 and λ = 0.02V-1. For VDS = 2V. What is the value of the drain current if both L and W are doubled?
a) 408 µA
b) 412 µA
c) 416 µA
d) 420 µA
View Answer

Answer: a
Explanation:
The value of the drain current is 408 µA if both L & W are doubled

9. A depletion type N channel MOSFEt with knW/L = 2 mA/V2 and Vt = 3V has its source and gate grounded. For Vd = 0.1V and neglecting channel length modulating effect. Find drain current.
a) 1.18 mA
b) 0.89 mA
c) 0.59 mA
d) 0.3 mA
View Answer

Answer: b
Explanation:
The drain current is 0.89 mA for type N channel MOSFEt with knW/L = 2 mA/V2 & Vt = 3
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10. A depletion type N channel MOSFEt with knW/L = 2 mA/V2 and Vt = 3V has its source and gate grounded. For Vd = 0.1V and neglecting channel length modulating effect. In which region is the triode operating?
a) Triode region
b) End of saturation region
c) Saturation region
d) None of the mentioned
View Answer

Answer: a
Explanation:
Triode region is the triode operating for type N channel MOSFEt with knW/L = 2 mA/V2

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

To practice all areas of Electronic Devices and Circuits Problems, 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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