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(EESM501)[2009](f)midterm~1833^_76648.pdf
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HONG KONG UNIVERSITY OF SCIENCE AND TECHNOLOGY
Department of Electronic and Computer Engineering
EESM 501 - CMOS VLSI Design
Fall 2009

October 22, 2009
STUDENT NUMBER: FAMILY NAME: FIRST NAME:

Write your student number, family name, and first name (no acronyms).
Copy sheets and books are NOT permitted.

SOLUTION

You cannot leave the exam room within the last 10 minutes of the exam.
Q1 (13pt)
Write the saturation current equation for a PMOS transistor including the channel length modulation effect
(2pt). Determine the boundary condition between the linear and saturation regions of operation (2pt).
Identify 6 physical and 3 voltage parameters that determine the current produced by a PMOS transistor
(4.5pt). Determine how each parameter needs to change (increase or decrease) to enhance the current
produced by a PMOS transistor (4.5pt).

Boundary condition between linear and saturation regions
2pt
PMOS saturation current equation: V = V .V
= V . V =
V .V
GD GS DS TPMOS DS GS TPMOS
1 ox W 2
2pt ISD =p (VGS .VTPMOS ) (1+VDS )2 tL
ox eff
V V (or V V .V )
GD TPMOS DS GS TPMOS
0.5pt
What is Voltage Parameter 1? VGS Should it increase or decrease for a faster transistor? Decrease (higher |VGS|) 0.5pt
0.5pt
What is Voltage Parameter 2? VDS
Should it increase or decrease for a faster transistor? Decrease (higher VSD) 0.5pt
0.5pt
What is Voltage Parameter 3? VTPMOS
Should it increase or decrease for a faster transistor? Increase (lower |VTPMOS|)

0.5pt
What is Physical Parameter 1? Hole mobility Should it increase or decrease for a faster transistor? Increase 0.5pt
0.5pt
What is Physical Parameter 2? Dielectric constant of the gate insulator Should it increase or decrease for a faster transistor? Increase
0.5pt
0.5pt
What is Physical Parameter 3? Thickness of gate oxide Should it increase or decrease for a faster transistor? Decrease

What is Physical Parameter 4? Channel width 0.5pt
Should it increase or decrease for a faster transistor? Increase 0.5pt
What is Physical Parameter 5? Channel length 0.5pt
Should it increase or decrease for a faster transistor? Decrease 0.5pt
0.5pt

What is Physical Parameter 6? Channel length modulation coefficient Should it increase or decrease for a faster transistor? Decrease (higher ||) 0.5pt
Q2 (30pt) Use the following table to answer the following question.

* Equivalent resistance extracted for |VGS| = VDD and |VDS| = VDD VDD/2
Consider the following circuit operating at a supply voltage of 1V.

Output = (A + B) . C . D

2pt
(b) (8pt) Size all the transistors to achieve equivalent resistance of 30k on all the worst-case pullup and pulldown paths. Assume all the transistors have minimum channel length. Determine the transistor widths in m.
Each correct transistor size is 1pt
1pt 30k
35k
RN1 = RN 2 = RN3 = RN 4 == 10k. WN1 = WN 2 = WN3 = WN 4 = 0.25m * = 0.875m
3
10k 1pt 1pt