IEEE Solid-States Circuits Magazine - Fall 2021 - 153

He was also fascinated by Tellegen's
theorem, which he and his colleagues
generalized [4] so that it can
be applied to operated variables,
such as differentiated, Fourier- or
Laplace-transformed,
and wave
variables. They also wrote a book
on the same subject [5].
In his 1966 paper titled " Circuit
Theory of Periodically Driven Nonlinear
Systems, " Penfield developed
a framework for periodically driven
nonlinear networks with small perturbations
[6].
In the 2016 paper
" Oscillator Phase Noise: A 50-Year
Review " [7], author D.B. Leeson
noted, " The Penfield paper showed
that subject only to conditions that
were typically met
in oscillators,
small AM [amplitude modulation]
and PM [phase modulation] noise
in a nonlinear circuit driven by a
periodic input could be treated as
strictly linear and stochastic, and
thus could be described in terms
of spectral densities. " This work was
found to enable the noise analysis
and simulation of many circuits,
including sampled-data analog
circuits, oscillators, and frequency
multipliers, that would otherwise
have been intractable.
Well before varactors found a
common application, Penfield foresaw
their usefulness and analyzed
their maximum cutoff frequency [8]
and noise [9]. He eventually wrote a
book on varactor applications with
R. Rafuse [10], which is still followed
by many field engineers. Thomas
Crowe, president and CEO of Virginia
Diodes, Inc., and Jeffrey Hesler,
CTO, write,
Varactor Applications (Penfield
and Rafuse) was initially published
nearly 60 years ago.
It
was considered essential for
circuit designers and is still
known today for its clarity
and completeness in covering
the range of varactor circuit
applications. Even today, in a
world dominated by powerful
computer-aided simulation and
design tools, the experts in the
field continue to use the design
equations from Varactor Applications
in developing state-ofthe-art
terahertz sources.
The insights from the design
in Penfield's work
equations
give accurate predictions of the
efficiency and required embedding
impedances to achieve the
best performance for varactor
multipliers. If a computer-aided
simulation of a varactor multiplier
disagrees with Varactor
Applications, then the engineer
should likely double check the
simulation for errors! Varactor
Applications continues to help
accelerate the pace of terahertz
circuit development, and it is
quite rare for an engineering
text to maintain such a relevance
after 50 years.
Penfield also made substantial
contributions to the area of computerintegrated
manufacturing for semiconductors,
an area he called CAF.
Based on analogies with the thriving
university software developments
and sharing of implementations in
electronic CAD, he spearheaded the
fostering of a multiuniversity community
of researchers and university fab
facilities to systematize and advance
the ability to represent, model, control,
automate, and support flexible
fabrication both in university fabs
and more broadly.
With collaborators at MIT;
the
University of California, Berkeley;
and Stanford, he led the joint definition
of requirements for CAF [11]
that became the basis for a substantial
program funded by DARPA to
prototype and implement such an
architecture. At MIT, the resulting
development of the CAF environment
[12] was both a research prototype
and the system that all staff,
students, and researchers using the
microfabrication facilities at MIT
depended on for their work.
Research contributions from this
effort included work on process flow
languages to represent the fabrication
process [13], with interpreters for
connecting to process simulators to
help with the design of the process,
downloading recipes, and running
equipment as well as tracking and
scheduling jobs in the fab. Additional
contributions included advancements
in run-by-run control, scheduling, and
processing modeling for semiconductor
and microelectromechanical systems
fabrication [14], [15].
Penfield's leadership in cultivating
an active university community in the
1980s continues to have impact, with
the evolution of software systems in
use to this day across university fabs
as well as an ethos of mutual support
among university, government, and
other research fabrication facilities.
His meaningful contributions to the
field were recognized with the Centennial
Medal from IEEE in 1984, the
IEEE Circuits and Systems Society Darlington
Prize Paper Award in 1985, and
the IEEE Circuits and Systems Society
Golden Jubilee Award in 1999 as well
as election to Fellow of IEEE and membership
in the National Academy of
Engineering, Sigma Xi, IEEE Antennas
and Propagation Society, Association
for Computing Machinery, and Audio
Engineering Society.
On a more personal note, Penfield
was devoted to his family, whose
growth and successes he chronicled
with pride, as well as his hometown
of Weston, Massachusetts, where he
championed the development of an
ecologically sound rail trail through
town. He was a beloved mentor
to many of us. Horowitz, Yahoo!
Founders Professor in the School of
Engineering at Stanford University,
remembers,
I was one of the many fortunate
MIT students who greatly
benefited from my interaction
with Penfield during time at
MIT. I also was lucky and able
to work with him again while
I was a Ph.D. degree student
at Stanford. I first interacted
closely with Penfield during
his efforts to bring work on
silicon ICs to campus. As hard
as it might be to believe, back
in the early 1970s, while I was
an undergraduate, there was
no work in silicon ICs done on
campus. To do research in that
area, I ended up working at Lincoln
Laboratory.
IEEE SOLID-STATE CIRCUITS MAGAZINE
FALL 2021
153
IEEE Solid-States Circuits Magazine - Fall 2021

Table of Contents for the Digital Edition of IEEE Solid-States Circuits Magazine - Fall 2021
