News - published on 27 April 2024

In Memoriam Prof. dr. ir. Willy Sansen (05/1943 – 04/2024)

The MICAS chip design research group from KU Leuven is mourning. Our founder and shining example, Willy Sansen, has passed away on April 25, 2024. Willy Sansen was a beacon in analog IC design research and education for the past 50 years. Willy Sansen was a true professor: a researcher and an educator.

Willy Sansen, the researcher

In one sentence, Willy Sansen’s research can be summarized as: enabling systematic analog circuit design in a digital, CMOS dominated, world. And that in all its aspects. He has shown how to start a design from transistor-level models, founded in solid-state physics, move on to larger building blocks like opamps or OTAs, and finally end up in fully integrated analog systems, such as filters, A/D-D/A converters, and all other kinds of analog signal processing blocks. This is now standard practice, but Willy Sansen was one of the founders of this systematic approach. He complemented this in the early days with analog CAD research. In the eighties, a time where almost all design went digital, Willy Sansen kept investing in analog research. His vision was already back then that, the more accurate and high-performant the digital processors become, the more accurate and high-bandwidth analog signals will be needed. A vision that materialized in the last decades.

Willy Sansen enjoyed all kinds of analog circuits, but he definitely had a fascination for the analysis of nonlinear distortion. Nonlinear distortion already played a role in Sansen’s own PhD, which he obtained in 1972 at UC Berkeley in California with Bob Meyer as adviser. Later, he studied harmonic and intermodulation distortion in nearly every circuit you can think of. His love for music, being a gifted player of the clarinet himself, probably rooted in the same grounds: distortion and harmonics are key to create a balanced sound. Analog building blocks and their systematic design are definitely the central theme in Sansen’s research, but he also cared for the relevance and application of analog circuits. That is where the love of biomedical electronic systems undoubtedly came from. Willy was the driving force behind the design of an early platform for a biomedical measurement and stimulation system: the Internal Human Condition System (IHCS). He was broadminded enough to incorporate the digital innovations of those days on it: a microprocessor! Willy Sansen was also a pioneer in the development of fully integrated stimulation drivers for the early cochlear implants.

Willy Sansen, the educator

Willy Sansen was a gifted teacher. Anyone who ever attended one of his classroom lectures, or one of his conference speeches, will forever remember it. His charismatic style was fascinating and inspiring. For the content of his classes, as for his research, systematic is also the keyword. Willy Sansen understood the art of building concepts that students initially experience as difficult – circuit stability is a good example – from the ground up, highlighting the basic principles and gradually increasing the complexity. At the end of the road, as the student or attendee, you just saw the light! His talent and drive for education has culminated in the book “Analog Design Essentials” (Springer, 2006). Most probably the bible for many generations of analog circuit designers to come. It is less known that this actually was his second book. The first one, entitled “Design of Analog Integrated Circuits and Systems”, was co-authored with Kenneth Laker. It had a somewhat more system-level focus, but it is also a classic. It first introduced the pole-zero position plots that Willy Sansen came up with to explain the frequency behavior of analog circuits as a function of several design parameters. Willy was also innovative when it came to educational technology. Decades before the pandemic forced everyone to record classes, Willy Sansen already made his courses available on video tape. Sansen was teaching at KU Leuven, Belgium, from 1972 till he became an emeritus professor in 2008. But Willy Sansen was not only teaching on the home front: he must have flown many times around the globe to visit universities and companies almost everywhere on earth to educate and to inspire students and starting engineers in analog circuit design.

Willy Sansen at the international scene

We already mentioned it for his teaching activities, but Willy Sansen has always been playing at international level. His Berkeley PhD laid the foundations for an international network that spans the globe. Throughout the years, he was a visiting professor in Philadelphia, Pennsylvania (USA), Ulm, Villach and Munich (all Germany). He has been on the technical committees of many conferences. He became even the first European program chair (in 2002) of the International Solid-State Circuits Conference (ISSCC), the most prestigious conference in IC design. Later on, in 2008-2009, he served as the first European president of the IEEE Solid-State Circuits Society (SSCS). Willy Sansen received many awards and honors in his career, from academy and industry, but the most distinctive award, and the one he was most proud of himself, is the 2011 IEEE SSCS Donald O. Pederson Solid-State Circuits Award.

Willy Sansen’s legacy

When Sansen retired from active duty at KU Leuven in 2008, having supervised 65 Ph.D. theses and having (co)authored more than 650 papers and 16 books. He left behind a well-established research group: MICAS (MICroelectronics And Sensors). The group today consists of six full-time professors and more than 50 Ph.D. students, who focus on the topics that Willy Sansen spent investigating throughout his entire career: analog and mixed-signal integrated circuit design, analog CAD methodologies, RF and microwave circuit design. Even digital design found its way into the group, always with a focus on circuit design and implementation, our core business. It should also be mentioned that Willy Sansen played an active role in the creation of six spin-off companies in his career. It is our challenge to maintain and further develop the high standards set by Willy Sansen and to let him live on in our ever-continuing research towards integrated “circuits for a better life”. But, at this moment, our thoughts are with Willy’s family, his daughters and his grandchildren. We want to offer them our most sincere condolences.

by W. Dehaene, M. Steyaert, G. Gielen, P. Reynaert, F. Tavernier, M. Verhelst

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