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ECE 124d/256c
Homework 3
Due: Wed Jan. 26, 2011
Reading: Buffer Paper, Penrose Paper (on line) Ref: Bakoglu, Elmore
Problems: (Note, you may find these problems are a bit deeper than previous ones  start earlier
to size them up and describe any simplifying assumptions you make.)
1. The repeater optimization proposed by Bakoglu was based on a simple model of a driver in
which the output capacitance of the driver is ignored. If the output capacitance is proportional to
the driver size e.g. C
out
=
α
W for a given driver width, find a new optimal delay, size and spacing
rule.
2. In the buffer paper, it is noted that inverter pairs (i.e. noninverting buffers) seem to have better
jitter behavior than do simple inverters. On the other hand, they are slower. Quantify the speed
difference by finding time optimal solutions for driver sizing and spacing as follows:
a. assuming minimum length, let the width of the first and second buffers be a and b respectively.
Find an expression for the total delay given a,b, spacing and the wire parameters.
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