nMOS and Complementary MOS (CMOS) MCQ Quiz – Objective Question with Answer for nMOS and Complementary MOS (CMOS) in VLSI

11. The switching threshold voltage VTH for an ideal inverter is equal to:

A. (VDD-VOL)/2
B. VDD
C. (VDD)/2
D. 0

Answer: C

The switching threshold voltage VTH for an ideal inverter is equal to (VDD./2.

12. The electrical equivalent component for MOS structure is:

A. Resistor
B. Capacitor
C. Inductor
D. Switch

Answer: B

The MOS structure acts as a capacitor with a metal gate and semiconductor acting as parallel plate conductors and oxide as a dielectric between them.

13. The Fermi potential is the function of:

A. Temperature
B. Doping concentration
C. Difference between Fermi level and intrinsic Fermi level
D. All of the mentioned

Answer: D

The Fermi potential, which is a function of temperature and doping, denotes the difference between the intrinsic Fermi level and the Fermi level.

14. The direction of the electric field when the gate voltage is zero:
A. Metal to semiconductor
B. Semiconductor to metal
C. No electric field exists
D. None of the mentioned

Answer: A

Metal is more positive compared to semiconductors. The electric field exists from metal to semiconductor.

15. Consider a MOS structure with equilibrium Fermi potential of the doped silicon substrate is given as 0.3eV. The electron affinity of Si is 4.15eV and metal is 4.1eV. Find the built-in potential of the MOS system.

A. -0.8eV
B. 0.8eV
C. 0.9eV
D. -0.9eV

Answer: D

Surface potential: qΦs = 4.15eV + 0.55eV + 0.3eV = 5.0eV
qΦm-qΦs = 4.1eV – 5.0eV = -0.9eV.

16. When the gate voltage is negative for enhancement mode n-MOS, the direction of the electric field will be:

A. Metal to semiconductor
B. Semiconductor to metal
C. No field exists
D. None of the mentioned

Answer: B

When the gate voltage is negative, holes in the substrate are attracted toward the surface creating an electric field from semiconductor to metal.

17. At threshold Voltage, the surface potential is:

A. Fermi potential
B. Fermi potential
C. 2 Fermi potential
D. -2 Fermi potential

Answer: A

When surface potential reaches –fermi potential, the surface inversion occurs. The gate voltage which brings these changes is known as the threshold voltage.

18. Surface inversion occurs when the gate voltage is:

A. Less than zero
B. Less than the threshold voltage
C. Equal to the threshold voltage
D. Greater than the threshold voltage

Answer: C

Surface inversion occurs when the gate voltage is equal to the threshold voltage.

19. For enhancement mode n-MOSFET, the threshold voltage is:

A. Equal to 0
B. Greater than zero or Positive quantity
C. Negative voltage or lesser than zero
D. All of the mentioned

Answer: B

For enhancement mode n-MOSFET, the threshold voltage is a positive quantity.

20. The threshold voltage depends on:

A. The work function difference between gate and channel
B. The gate voltage component to change surface potential
C. The gate voltage component to offset the depletion charge and fixed charges in gate oxide
D. All of the mentioned

Answer: D

The threshold voltage depends on: The work function difference between gate and channel, The gate voltage component to change surface potential, The gate voltage component to offset the depletion charge, and fixed charges in the gate oxide.

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