Singularities of Nonlinear Circuit Theory and Applications: Achievements of Professor Leon Ong Chua

Professor Leon O. Chua is globally recognized as a profound founder of modern nonlinear circuit theory and original researcher. It was my personal fortune to become one of Leon's early graduate students at the University of California, Berkeley in 1972 soon after his move to UC Berkeley from Purdue University. The Circuits and Systems faculty at that time included late professors Ernest Kuh, Charles Desoer and professors Lofti Zadeh, Elijah Jury, and Lucien Polak, among others. The Integrated Circuits faculty was consisted of late professor Donald Peterson and professor David Hodges, and their associates. Leon?s graduate research group included Robert Schilling, Douglas Green, formerly of UCLA, John Wyatt of MIT, and some years later Stephen Boyd of Stanford University, Michael Peter Kennedy of the University College Cork, Ireland, and Chai Wah Wu of IBM Yorktown Heights, NY. His brilliance and passion for research attracted many talents. For CAS Society Leon hosted the 1974 San Francisco ISCAS and served as president in 1977. I met many distinguished visitors and many of them have become life-long colleagues- to mention a few, professor Timothy Trick of the University of Illinois at Urbana-Champaign, late professor Tamas Roska from Hungary, professor Akio Ushida of Tokushima University, Japan. It is difficult to list Leon's life-long achievements in a limited space. Here I will try to describe a subset that I have had some involvement under Leon's guidance. My own research topics included modeling of nonlinear devices and systems. The world of nonlinear circuits and systems is considered broad and Leon's research strategy was to classify and investigate particular classes of nonlinear systems. Leon's first book on nonlinear network theory [1] describes specific nonlinear systems. One of projects that I was initially worked on was on development of a canonical representation of piecewise linear functions using a combination of linear functions, absolute value functions with different breakpoints and jump discontinuities as [2]