Nonlinearities: Your worst enemies…? … Your best friends!

This paper explores the problem of nonlinearities encountered in electronic circuits and systems. Nowadays commonly used by engineers are models and methods belonging to linear toolkit despite the fact that all real-world circuit elements are inherently nonlinear. We discuss the problems associated with nonlinear approach and consequences for circuit analysis and design. We stress also the fact that although in many applications the linear operation principle is of paramount importance and we make every effort to design the circuitry to operate as closely as possible to linear, there exist a vast area of applications where the nonlinearities make the circuit operation possible!