IEEE Solid-States Circuits Magazine - Fall 2021 - 154

Penfield realized this was a
mistake, and, back in 1977, he
helped organize a class on IC
design for MIT professors and a
few students in this area. This
course was taught by Botchek,
an IC design consultant. I was
a lucky student who took the
class and got to see my MIT professors
in a new light. Penfield,
in particular, seems to delight
in learning new concepts.
It was an amazing experience
for me, and I have tried to
replicate Penfield's interest in
lifelong learning in my career.
It also convinced Penfield and
others to bring VLSI design to
campus, which started when
Lynn Conway taught a VLSI
design course in 1978. This
push changed the course of
EECS research at MIT. Silicon
ICs have driven the information
revolution, and, as a result
of this change, MIT has been
one of the key research centers
driving this effort.
Mostly because I got to know
Penfield during the VLSI class,
I reached out to him while I
was doing my Ph.D. degree
research. He had just published
a paper on bounding the
delay in RC trees, which could
be used to estimate delays in
CMOS circuits. For my Ph.D.
degree, I was trying to extend
their work to handle a nonlinear
model of an MOS device. I
was close to a solution, but I
couldn't understand how they
did one step in their algorithm.
Penfield explained that they
didn't have a forward path for
that step, but they guessed the
answer, and could prove that
it worked, which was great for
them, but didn't help me.
After working on it for a
(long) while, I did come up with
a forward path, which solved
my problem and allowed me to
improve their delay bounds. I
excitedly wrote Penfield to tell
him about my results. He was
genuinely excited and wrote
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FALL 2021
back about how he was able to
improve on them!
I learned a great lesson from
this exchange. First, the importance
of sharing work freely and
being open to improvements on
your work-we both benefited
from the exchange. The second
lesson was probably more
important for me: don't worry
about who invented what when
working in a team. Many people
can invent the same thing, and,
in collaboration, it never really
matters who invented it first.
While I am sure that Penfield
knew this instinctively, I
initially was less gracious than
Penfield when he improved my
results. Fortunately for me,
since I knew Penfield was such
a nice guy, I had that argument
only internally, learned my lesson,
and responded in a gracious
way. As a result of this
exchange, Penfield added me as
a coauthor to the journal paper
about this method (which won
the Darlington Paper Award),
which was a better result than I
could have ever hoped for. Penfield
was an amazing teacher
and mentor. I will miss him.
Penfield's passion for getting to
what is right, rather than being right,
also made him a good shepherd for
junior faculty. As department head,
Penfield was responsible for assembling
promotion cases, a process
that begins by convening senior faculty
to collect input. As Prof. Jacob
White, Cecil H. Green Professor of
EECS recalls, " These meetings were
often nodding consensuses followed
by silence, leaving Penfield without
the specifics he needed to make compelling
cases. To spark discussion,
Penfield was always willing to serve
as devil's advocate, and I always picture
him as frantically taking notes
as his colleagues rapidly fired their
detailed rebuttals. "
For Penfield, changing his mind in
response to a compelling argument
was about more than just getting to
the right answer. He clearly enjoyed,
even took pride in, being correctly
IEEE SOLID-STATE CIRCUITS MAGAZINE
contradicted, a trait that was an
important early influence on White.
" Junior faculty are told that doctoral
students should stand on your shoulders
and see further, but it is very different
when your student shows that
you got it wrong. Having one's ideas
overturned, it is so easy to respond
defensively, but I had Penfield as a
role model and could recognize this
as a milestone worth celebrating. " We
will all miss you, Paul.
References
[1] P. Paul, J. Guttag, C. Searle, and W. Siebert,
" Shifting the boundary: A professional
master's program for 2000 and beyond, "
in Proc. 1992 Front. Education Conf., Nashville,
TN, pp. 645-649.
[2] P. Paul Jr. and J. Rubinstein, " Signal delay
in RC tree networks, " in PIWC 18th ACMIZEEE
Design Automat. Conf., June 1981,
pp. 613-617.
[3] J. Rubinstein, P. Paul, and M. Horowitz,
" Signal delay in RC tree networks, " IEEE
Trans. Comput.-Aided Design, vol. 2, no. 3,
pp. 202-211, July 1983. doi: 10.1109/
TCAD.1983.1270037.
[4] P. Paul Jr., R. Spence, and S. Duinker, " A
generalized form of Tellegen's Theorem, "
IEEE Trans. Circuit Theory, vol. 17, no. 3,
pp. 302-305, Aug. 1970. doi: 10.1109/
TCT.1970.1083145.
[5] P. Paul Jr., R. Spence, and S. Duinker, Tellegen's
Theorem and Electrical Networks.
Cambridge, MA: MIT Press, 1970.
[6] P. Paul, " Circuit theory of periodically
driven nonlinear
systems, " Proc.
vol. 54, no. 2, pp. 266-280, Feb. 1966.
[7] D. B. Leeson, " Oscillator phase noise: A
50-year review, " IEEE Trans. Ultrason.
Ferroelectr. Freq. Control, vol. 63, no. 8,
pp. 1208-1225, Aug. 2016. doi: 10.1109/
TUFFC.2016.2562663.
[8] P. Paul Jr., " Maximum cutoff frequency
of varactor diodes, " Proc. IEEE, vol. 53,
pp. 422-423, Apr. 1965.
[9] P. Paul, " The minimum noise of varactor
amplifiers, " IRE Trans. Military Electron.,
vol. MIL-6, pp. 320-325, Oct. 1962.
[10] P. Paul and R. Rafues, Varactor Applications.
Cambridge, MA: MIT Press, 1964.
[11] P. Paul Jr. et al., " Requirements for computer-aided
fabrication, " MIT VLSI Memo,
no. 84-200, Jan. 17, 1984.
[12] M. B. McIlrath, D. E. Troxel, M. L. Heytens,
P. Paul Jr., D. S. Boning, and R. Jayavant,
" CAFE-The
MIT computer-aided
fabrication environment, " IEEE Trans.
Components, Hybrids, Manuf. Technol.,
vol. 15, no. 3, pp. 353-360, May 1992. doi:
10.1109/33.148503.
[13] D. S. Boning, M. B. McIlrath, P. Paul Jr., and E.
M. Sachs, " A general semiconductor process
modeling framework, " IEEE Trans. Semiconductor
Manuf., vol. 5, no. 4, pp. 266-280,
Nov. 1992. doi: 10.1109/66.175359.
[14] P. Paul Jr., D. A. Antoniadis, S. B. Gershwin,
E. M. Sachs, and S. D. Senturia, " Computeraided
fabrication system implementation, "
Defense Tech. Information Center, Final
Tech. Rep., ADA213005, Dec. 1988.
[15] P. Paul Jr., D. A. Antoniadis, S. B. Gershwin,
S. D. Senturia, and E. M. Sachs, " Computer-aided
fabrication of integrated circuits, "
Defense Tech. Information Center,
Final Tech. Rep., ADA215439, Sept. 1989.
IEEE,
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