Electronic Devices and Circuits Questions and Answers – MOSFETs Circuits at DC

This set of Tough Electronic Devices and Circuits Questions and Answers focuses on “MOSFETs Circuits at DC”.

1. The transistor in the circuit shown below has kn = 0.4 mA/V2, Vt = 0.5 V and λ = 0. Operation at the edge of saturation is obtained when
Operation of saturation obtained when (W/L)RD = 1.5 kΩ for transistor with kn is 0.4 mA/V2
a) (W/L)RD = 0.5 kΩ
b) (W/L)RD = 1.0 kΩ
c) (W/L)RD = 1.5 kΩ
d) (W/L)RD = 2.0 kΩ
View Answer

Answer: c
Explanation: Use the standard formula for edge saturation.

2. The PMOS transistor in the circuit shown has Vt = −0.7 V, μpCox = 60 μA/V2, L = 0.8 μm, and λ = 0. Find the value of R in order to establish a drain current of 0.115 mA and a voltage VD of 3.5 V.
Find value of R in order to establish drain current of 0.115 mA & voltage VD of 3.5 V
a) 12.5 KΩ
b) 25 kΩ
c) 37.5 kΩ
d) 50 kΩ
View Answer

Answer: a
Explanation:
Value of R in order to drain current of 0.115 mA & voltage VD of 3.5 V is 12.5 KΩ

3. The NMOS transistors in the circuit shown have Vt = 1 V, μnCOX = 120 μA/V2, λ = 0, and L1 = L2 = L3 = 1μm. Then which of the following is not the value of the width of these MOSFETs shown
a) 2 µm
b) 8µm
c) All of the mentioned
d) None of the mentioned
View Answer

Answer: d
Explanation:
Find value of width of MOSFETs if NMOS transistors in have Vt = 1 V, μnCOX = 120 μA/V2

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4. The MOSFET shown has Vt = 1V, kn = 100µA/V2 and λ = 0. Find the required values of W/L and of R so that when vI = VDD = +5 V, rDS = 50 Ω, and VO = 50 mV.
Find values of W/L & of R when vI = VDD = +5 V, rDS = 50 Ω, & VO = 50 mV
a) W/L = 25 and R = 4.95 kΩ
b) W/L = 25 and R = 9.90 kΩ
c) W/L = 50 and R = 4.95 kΩ
d) W/L = 50 and R = 9.90 kΩ
View Answer

Answer: c
Explanation:
Values of W/L & of R so rDS = 50 Ω, & VO = 50 mV is W/L = 50 & R = 4.95 kΩ

5. For each of the circuits shown find the labeled voltages. For all transistors, kn(W/L) = 1 mA/V2, Vt = 2V, and λ = 0. Find V3
Find V3 for all transistors, kn(W/L) = 1 mA/V2, Vt = 2V, & λ = 0
a) 2.41V
b) 3.41V
c) 4.41V
d) 1.41V
View Answer

Answer: b
Explanation: V3 = 10- 4 * 2 + 1.4 = 3.4v.
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6. For each of the circuits shown find the labeled voltages. For all transistors, kn(W/L) = 1 mA/V2, Vt = 2V, and λ = 0. Find V4 and V5
Find V4 & V5 for all transistors, kn(W/L) = 1 mA/V2, Vt = 2V, & λ = 0
a) 4V and -5V respectively
b) -4V and 5V respectively
c) 4V and 5V respectively
d) -4V and -5V respectively
View Answer

Answer: a
Explanation: The V4 & V5 is 4V & -5V for all transistors, kn(W/L) = 1 mA/V2, Vt = 2V, & λ = 0

7. For each of the circuits shown find the labeled voltages. For all transistors, kn(W/L) = 1 mA/V2, Vt = 2V, and λ = 0. Find V1 and V2
a) 2V and -4V
b) -2V and 4V
c) 2V and 4V
d) -2V and -4V
View Answer

Answer: c
Explanation: ID = 1 = 12 * 1 * (VGS – 2)2 => VGS = 3.41v.
V3 = 3.41v.
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8. For each of the circuits shown find the labeled node voltages. The NMOS transistors have Vt = 1 V and kn( W/L ) = 2 mA/V2 and λ = 0. Find V1 and V2
Find V1 & V2 for NMOS transistors have Vt = 1 V & kn(W/L) = 2 mA/V2 & λ = 0
a) 2.44 and -1.28 V
b) 2.44 and -2.56 V
c) 1.22 and -2.56 V
d) 1.22 and -1.28 V
View Answer

Answer: b
Explanation:
V1 & V2 is 2.44 & -2.56 V if NMOS transistors have Vt = 1 V & kn(W/L) = 2 mA/V2

9. For each of the circuits shown find the labeled node voltages. The NMOS transistors have Vt = 1 V and kn( W/L ) = 2 mA/V2 and λ = 0. Find V3 and V4
Find V3 & V4 if NMOS transistors have Vt = 1 V & kn(W/L) = 2 mA/V2 & λ = 0
a) 3.775V and 5V
b) 3.775V and 2.55V
c) 7.55V and 2.55V
d) 7.555V and 5V
View Answer

Answer: d
Explanation:
V3 & V4 if NMOS transistors have Vt = 1 V & kn(W/L) = 2 mA/V2 is 7.555V & 5V
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10. For the PMOS transistor in the circuit shown kn= 8 µA/V2, W/L = 25,|Vtp| = 1V and I = 100μA. For what value of R is VSD = VSG?
Find value of R if VSD = VSG for PMOS transistor in the circuit shown kn= 8 µA/V2
a) 0 Ω
b) 12.45 kΩ
c) 25.9 kΩ
d) 38.35 kΩ
View Answer

Answer: a
Explanation: VSG will be equal to VSD only when the resistance shown is zero or in other words there should not be any resistance.

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

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

If you find a mistake in question / option / answer, kindly take a screenshot and email to [email protected]

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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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