# VLSI Questions and Answers – Limitations of Scaling -2

This set of VLSI Questions and Answers for Experienced people focuses on “Limitations of Scaling -2”.

1. Maximum transit time occurs when the size of the transistor is
a) minimum
b) maximum
c) does not depend on size
d) double

Explanation: Maximum transit time occurs when the size of the transistor is minimum when Va is approximately 0.

2. The spacing of interconnect is scaled by
a) α
b) 1/α
c) α2
d) 1/α2

Explanation: Spacing of interconnect, width and thickness are scaled by 1/α as they are linear dimensions.

3. Cross section area is scaled by
a) α
b) 1/α
c) α2
d) 1/α2

Explanation: Cross section area is scaled by 1/α2 as area is the product of length and width which are scaled by 1/α.

4. The decrease in device dimension ______ the die size.
a) increases
b) decreases
c) does not affect
d) decreases and then increases

Explanation: The decrease in device dimension increases the die size and also the levels of integration.

5. The reduction in die size reduces
a) R
b) d
c) L
d) W

Explanation: The reduction in die size also reduces R and C. Die size depends on both resistor and capacitor.
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6. The propogation delay along the optical fiber interconnect can be given as
a) n/Lx
b) nL/c
c) c/nL
d) nc/L

Explanation: The propogation delay along the optical fiber interconnect can be given as nL/c where n is the refractive index, L is the length of the fiber and c is the speed of light.

7. The breakdown voltage can be reduced by _____ electric field strength.
a) increasing
b) decreasing
c) does not depend
d) exponentially decreasing

Explanation: The increase in electric field strength lowers the breakdown voltages. Electric field is inversely proportional to the voltage.

8. Greater the switching speed _____ is the more.
a) low
b) more
c) all of the mentioned
d) none of the mentioned

Explanation: Increase in switching speed increases the noise problems. Switching speed is the rate a which the logic level varies.

9. Substrate concentration is scaled by
a) α
b) 1/α
c) α2
d) 1/α2

Explanation: Substrate concentration Nb which gives the doping level of substrate is scaled by α.

10. The increase in operating frequency results in ______ in cross-talk noise.
a) increase
b) decrease
c) no change
d) doubling

Explanation: The increase in operating frequency and reduction in rise time tr results in the increase of cross-talk noise.

11. Flicker noise is scaled by
a) 1/α2
b) α22
c) 1/β2
d) β22

Explanation: Flicker noise occurs due to fluctuations of carriers trapped in the channel by surface states. It is scaled by α22.

12. Scaling affects _____ generated noise.
a) internally
b) externally
c) internally and externally
d) does not generate

Explanation: Scaling affects both internally and externally generated noise and this degrades both the production yeild and the reliability of high density chip layouts.

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