MOS Transistor Theory MCQ Quiz – Objective Question with Answer for MOS Transistor Theory

31. 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.

Hence the built-in potential of the MOS system is -0.9eV.

32. 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.

33. 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.

34. 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.

Inversion layer, surface inversion can be utilized for conducting current between two terminals of the MOS transistor.

35. 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.

36. 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 changes the surface potential
The gate voltage component to offset the depletion charge and fixed charges in the gate oxide

37. The expression for threshold voltage for the enhancement mode nMOSFET is:

A. Φgc-2ϕf-Qbo/Cox-Qox/Cox
B. Φgc+ϕf-Qbo/Cox
C. Φgc-ϕf-Qbo/Cox+Qox/Cox
D. Φgc+2ϕf-Qbo/Cox-Qox/Cox

Answer: A

The expression for threshold voltage for the enhancement mode nMOSFET is

Φgc-2ϕf-Qbo/Cox-Qox/Cox.

38. Noise Margin is:

A. Amount of noise the logic circuit can withstand
B. Difference between VOH and VIH
C. Difference between VIL and VOL
D. All of the Mentioned

Answer: D

Noise Margin is defined as the amount of noise the logic circuit can withstand, it is given by the difference between VOH and VIH or VIL and VOL.

39. The VIL is found from the transfer characteristics of the inverter by:

A. The point where the straight line at VOH ends
B. The slope of the transition at a point at which the slope is equal to -1
C. The midpoint of the transition line
D. All of the mentioned

Answer: B

The VIL is the input voltage at which the slope of the transition will be equal to -1.

40. The VIH is found from the transfer characteristic of the inverter by:

A. The point where a straight line at VOH ends
B. The slope of the transition at a point at which the slope is equal to -1
C. The midpoint of the transition line
D. All of the mentioned

Answer: B

The VIH is the input voltage at which the slope of the transition will be equal to -1. In Transfer characteristics at 2 points, we will find the slope to be -1.

Pages: 1 2 3 4 5 6

Related Posts