Memorial Tributes: Volume 26
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  • Jane Halpern
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  • PAUL L. PENFIELD JR. (1933-2021)



    PAUL LIVINGSTONE PENFIELD JR., pioneering educator and chronicler of entropy, died on June 22, 2021, at age 88.

    Paul was born May 28, 1933, in Detroit, Michigan, to Paul Livingstone Penfield of Detroit and Charlotte Wentworth (Gilman) Penfield of Birmingham, Michigan. A lifelong resident of Weston, Massachusetts, Paul’s devotion to his community was exceeded only by his dedication to his family, whose growth and successes he chronicled with pride as an amateur genealogist.

    Paul received a BA (cum laude) in physics from Amherst College in 1955, and an ScD in electrical engineering from the Massachusetts Institute of Technology (MIT) in 1960. He joined MIT’s faculty in the Department of Electrical Engineering and Computer Science (EECS) in 1960, serving as associate department head from 1974 to 1978 and department head from 1989 to 1999.

    As a departmental leader, Paul was instrumental in building up EECS’s activity in silicon integrated circuits. He played a key role in bringing Lynn Conway (NAE 1989) to EECS in 1978 as a visiting professor to teach the first large-scale integration system design course, culminating with student-designed integrated circuits that were fabricated by Hewlett-Packard. This launched not only a universally accepted syllabus, but also the concept of the MOSIS foundry.

    One of Paul’s most significant contributions to the EECS community was the development of Information, Entropy, and Computation, a course offered jointly by EECS and the Department of Mechanical Engineering for almost 20 years, helping to make the Second Law of Thermodynamics more accessible to first-year students by treating entropy as a form of information. His commitment to his students was fittingly commemorated with the Paul L. Penfield Student Service Award, granted to undergraduate and graduate students in honor of his devotion to the department. Another lasting contribution was Paul’s establishment of the Master of Engineering degree as an accessible and primary path for MIT EECS undergraduates, following (or integrated with) their bachelor’s degree. The EECS M. Eng program has been in place for more than two decades, and is currently the choice of more than two-thirds of the EECS undergraduates (and nearly a fifth of all MIT undergraduates).

    Paul was the director of the MIT Microsystems Research Center from 1985 to 1989 and the Dugald C. Jackson Professor of Electrical Engineering from 2000 until his retirement in June 2005. He also spearheaded the establishment of MIT’s Microsystems Technology Laboratories, which allowed MIT to reclaim a prominent national position in silicon technology.

    In 1996–97 he served as president of the National Electrical Engineering Department Heads Association (NEEDHA) and in March 2000 received its Outstanding Service Award. In 1998 he organized MIT’s Building 20 Commemoration, for which he received the 1999 Presidential Citation from the Association of Alumni and Alumnae of MIT.

    Paul’s wideranging research interests included inquiry into solid-state microwave devices and circuits, noise, and thermodynamics; electrodynamics of moving media; circuit theory; computer-aided design; APL language extensions; integrated-circuit design automation; computer-aided fabrication of integrated circuits; and the equivalence of information and thermodynamic entropy. His work with Jorge Rubinstein, later in collaboration with Mark Horowitz (NAE 2007), on the signal delay in RC tree networks set the upper and lower bounds of signal delay in tree networks such as complex MOS digital circuits. This work is considered seminal by many and has been extensively cited. The paper was awarded the Institute of Electrical and Electronics Engineers (IEEE) Circuits and Systems Society Darlington Prize Paper Award in 1985.1 His meaningful contributions to the field were also recognized with the Centennial Medal from IEEE in 1984 and the IEEE Circuits and Systems Society Golden Jubilee Award in 1999.2

    Paul also made substantial contributions to the area of computer-integrated manufacturing (CIM) for semiconductors, an area he called computer-aided fabrication (CAF). Based on analogies with the thriving university software developments and sharing of implementations in electronic CAD, he spearheaded the fostering of a multi-university community of researchers and university lab facilities to systematize and advance the ability to represent, model, control, automate, and support flexible fabrication both in university labs and more broadly. With collaborators at MIT, UC Berkeley, and Stanford, he led the joint definition of requirements for computer-aided fabrication, which became the basis for a substantial program funded by DARPA to prototype and implement such an architecture.

    Paul was a fellow of the IEEE and the International Engineering Consortium. He was also a member of the National Academy of Engineering, Sigma Xi, the American Physical Society, the Association for Computing Machinery, and the Audio Engineering Society. He has been a consultant for many companies, and between 1980 and 1995 he served as a director of GenRad, Inc.

    Outside of his incredible career in academia, Paul was a passionate environmentalist and member of the American Fern Society and the Hardy Fern Foundation. He cultivated a collection of ferns, beginning with spores in petri dishes, and planted the larger specimens in the garden around his home. One of Paul’s most notable contributions was his tireless championship of the development of an ecologically sound rail trail in Weston, where residents and visitors could hike and ride bikes in peaceful, wooded surroundings. He enthusiastically supported environmental organizations including the Lake George Land Conservancy, the Nature Conservancy, the Weston Forest and Trail Association, and the recently created MetroWest Climate Solutions Group.

    One of Paul’s greatest passions was his family. He is survived by his companion, Catherine Liddell, of Natick, Massachusetts; his sister Martha (Tyner) Brown of Virginia Beach, Virginia; three children, David (Rebecca Bronson) of Westford, Massachusetts (whose sons are Andrew and Scott), Patricia (Craig) Jonas of Denver, Colorado (whose son is Paul, named after his grandfather and great-grandfather), and Michael; four stepchildren, John (Joan)  Lory, Stephen Richards Lory, Carol Topp, and Cameron (Andrew) Faulds; and three grandchildren and six step-grandchildren. He was predeceased by his first wife Martha (Dieterle) Elise, his second wife Barbara (Buehrig Lory) Jean, and his sister Eleanor (Guilford Lawson II) Spencer.


    1Rubinstein J, Penfield P Jr., Horowitz MA. 1983. Signal delay in RC tree networks. IEEE Transactions on Computer-Aided Design of Integrated Circuits and Systems 2(3):202–211.
    2Information in this paragraph is from: Chandrakasan A, Lee H, Boning D, Ozdaglar A, White J, Horowitz M, Crowe T, Hesler J. 2021. In memory of Paul Penfield Jr. 
    (1933–2021). IEEE Solid States Circuit Magazine 13(4):151–154.