This set of VLSI Multiple Choice Questions & Answers (MCQs) focuses on “Limitations of Scaling -1”.
1. Built-in junction potential Vb depends on
c) substrate doping level
d) oxide thickness
Explanation: Built-in junction potential Vb depends on substrate doping level and this will be acceptable so long as Vb is small compared with Vdd.
2. As the channel length is reduced in a MOS transistor, depletion region width must be
c) must not vary
d) exponentially decreased
Explanation: As the channel length is reduced in a MOS transistor, depletion width must also be scaled down to prevent the source and drain depletion regions from meeting.
3. Vdd is scaled by
Explanation: Supply voltage Vdd is scaled by 1/β. All voltages are scaled by 1/β.
4. If doping level of substrate Nb increases then depletion width
c) does not change
d) increases and then decreases
Explanation: If the substrate doping length Nb increases then depletion width decreases because depletion width is inversely proportional to Nb.
5. Maximum electric field can be given as
Explanation: Maximum electric field can be given by 2V/d and this is induced in one-sided step junction.
6. The size of a transistor is usually defined in terms of its
a) channel length
b) feature size
d) thickness ‘d’
Explanation: The size of a transistor is usually defined in terms of its channel length L because feature size only gives area capacitance etc.
7. What is the minimum value of L to maintain transistor action?
Explanation: The channel length L should be atleast 2d to maintain the transistor action and to prevent punch-through.
8. L depends on
a) substrate concentration
Explanation: Channel length L depends on the supply voltage Vdd and substrate concentration Nb.
9. Drift velocity can be given as
c) µ * E
Explanation: Carrier drift velocity can be given as the product of µ and E and the maximum carrier drift velocity is approximately equal to Vsat regardless of supply voltage.
10. The transit time can be given as
Explanation: The transit time can be given by L/Vdrift which is equivalent to 2d/µE as L = 2d and Vdrift is µE.
Sanfoundry Global Education & Learning Series – VLSI.
To practice all areas of VLSI, here is complete set of 1000+ Multiple Choice Questions and Answers.