VLSI Design Questions and Answers - MOS Circuits Area Capacitance and Delay Unit

1. The junction parasitic capacitance are produced due to ____________
a) Source diffusion regions
b) Gate diffusion regions
c) Drain diffusion region
d) All of the mentioned

Answer: c
Explanation: The junction parasitic capacitance are produced due to drain diffusion capacitance

2. The amount of parasitic capacitance at the output node is determined by __________
a) Concentration of the impurity doped
b) Size of the total drain diffusion area
c) Charges stored in the capacitor
d) None of the mentioned

Answer: b
Explanation: The amount of parasitic capacitance is a linear function of drain diffusion area

3. The dominant component of the total output capacitance in submicron technology is?
a) Drain diffusion capacitance
b) Gate oxide capacitance
c) Interconnect capacitance
d) Junction parasitic capacitance

Answer: c
Explanation: Interconnect capacitance becomes dominant component in submicron technology.

4. Which of the following is dominant component in input capacitance?
a) Gate diffusion capacitance
b) Gate parasitic capacitance
c) Gate oxide capacitance
d) All of the mentioned

Answer: c
Explanation: For input capacitance, gate oxide capacitance is the main component.

5. The total load capacitance is calculated as the sum of __________
a) Drain capacitance in series with input capacitance
b) Drain capacitance + interconnect capacitance +input capacitance
c) Drain capacitance + interconnect capacitance – input capacitance
d) Drain capacitance in parallel with input capacitance

Answer: b
Explanation: Total load capacitance = Drain capacitance + interconnect capacitance +input capacitance

6. The interconnect capacitance is formed by __________
a) Area between the interconnect lines
b) Interconnect lines between the gates
c) Inter electrode capacitance of interconnect lines
d) None of the mentioned

Answer: b
Explanation: Interconnect line between the gates form interconnect capacitance.

7. The amount of gate oxide capacitance is determined by __________
a) Charges present on the gate
b) Polarity of the gate
c) Charges present on the substrate
d) Area of the gate

Answer: d
Explanation: The amount of gate oxide capacitance is determined by the area of the gate.

8. By what amount is Sidewall doping larger than substrate doping concentration.
a) 5
b) 2
c) 1
d) 10

Answer: d
Explanation: The sidewall doping is 10 times larger.

9. Zero bias depletion capacitance per unit length at sidewall junctions is given by, (Cj is the zero bias depletion capacitance per unit area).
a) (√10).Cj.xj
b) (√5).Cj.xj
c) (√10).Cj.xj2
d) (√10).Cj.xj3

Answer: a
Explanation: Since the doping concentration is 10 times larger.

10. The typical value of capacitance in pF x 10-4/µm2 for gate to channel in λ based design is?
a) 1
b) 0.4
c) 0.2
d) 4

Answer: d
Explanation: The gate to channel capacitance in λ based design is 4 pF x 10-4/µm2.