# 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

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

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.

a) 12.5 KΩ
b) 25 kΩ
c) 37.5 kΩ
d) 50 kΩ

Explanation:

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

Explanation:

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.

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

Explanation:

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

a) 2.41V
b) 3.41V
c) 4.41V
d) 1.41V

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

a) 4V and -5V respectively
b) -4V and 5V respectively
c) 4V and 5V respectively
d) -4V and -5V respectively

Explanation:

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

Explanation: ID = 1 = 12 * 1 * (VGS – 2)2 => VGS = 3.41v.
V3 = 3.41v.

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

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

Explanation:

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

a) 3.775V and 5V
b) 3.775V and 2.55V
c) 7.55V and 2.55V
d) 7.555V and 5V

Explanation:

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?

a) 0 Ω
b) 12.45 kΩ
c) 25.9 kΩ
d) 38.35 kΩ

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.

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