1. Diffusion capacitance is equal to ___________
a) area capacitance
b) peripheral capacitance
c) fringing field capacitance
d) area capacitance + peripheral capacitance
Explanation: Diffusion capacitance is given by the sum of area capacitance and peripheral capacitance.
2. Polysilicon is suitable for ___________
a) small distance
b) large distance
c) all of the mentioned’
d) none of the mentioned
Explanation: Polysilicon is unsuitable for routing Vdd or Vss other than for very small distance because of the relatively high Rs value of the polysilicon layer.
3. Which has a high voltage drop?
a) metal layer
b) polysilicon layer
c) diffusion layer
d) silicide layer
Explanation: Polysilicon layer has high voltage drop. It has a moderate RC product.
4. Which layer has high capacitance value?
a) metal
b) diffusion
c) silicide
d) polysilicon
Explanation: Diffusion or active layer has high capacitance value due to which it has low or moderate IR drop.
5. Which layer has high resistance value?
a) polysilicon
b) silicide
c) diffusion
d) metal
Explanation: Polysilicon layer has high resistance value and due to this it has high IR drop.
6. While measuring the output load capacitance Cgs, n and Cgs, p is not considered. Why?
a) Because Cgs, n and Cgs, p are the capacitances at the input nodes
b) Because Cgs, n and Cgs, p does not exist during the operation of CMOS inverter
c) Because Cgs, n and Cgs, p are storing opposite charges and cancel out each other during the calculation of load capacitance
d) None of the mentioned
Explanation: Cgs, n and Cgs, p are gate to source capacitances of nMOS and pMOS transistors in CMOS inverter. They are measured at input node. Therefore they are not considered for calculation of load capacitance
7. During the calculation of load capacitance of a 1st stage CMOS inverter, the input node capacitances, Cgs, n and Cgs, p of the 2nd stage CMOS inverter is also considered.
a) True
b) False
Explanation: Instead thin oxide capacitance over the gate area is used for calculation.
8. The resistance of uniform slab of the conducting material is?
a) Linear(proportional) with length
b) Inversely proportional to thickness
c) Inversely proportional to width
d) All of the mentioned
Explanation: The resistance of a uniform slab of conducting material can be expressed as
R = (ρ.l)/(t.w).
9. The sheet resistance of the conducting material is?
a) RS = resistivity/length
b) RS = resistivity/width
c) RS = resistivity/thickness
d) None of the mentioned
Explanation: The sheet resistance of the conducting material is given by RS = resistivity/thickness.
10. In CMOS manufacturing process Sheet resistance is used instead of resistivity because _______________
a) Resistivity is same for all doped regions
b) Resistivity and thickness are characteristics which cannot be controlled by the circuit designer, and it is expressed as the single sheet resistance parameter
c) Sheet resistance is dimensionless quantity
d) Sheet resistance is equal to resistivity
Explanation: It is convenient to use Sheet resistance instead of resistivity because Resistivity and thickness are characteristics which cannot be controlled by the circuit designer, and it is expressed as the single sheet resistance parameter.