Nonlinear behavior in active devices can lead to distortion and
lost information in communications systems that rely on those
devices. Because silicon CMOS transistors are so widely used in
analog, digital, and mixed-signal circuits, understanding the
nonlinear characteristics of these transistors can serve to
improve performance in highly integrated circuits (ICs). To that
end, a new transistor model was developed for high-frequency
silicon CMOS transistors, using a superposition method to
quantify the individual contributions of different nonlinear
elements.  The model is implemented entirely using symbolically
defined devices (SDDs) to represent each nonlinear parameter.
The real-life basis for the model is a 0.18-μm RF silicon CMOS
foundry device capable of operation to 10 GHz. With the help of
the Advanced Design System (ADS) suite of simulation software
tools from Agilent Technologies (, the SDD model will be
validated by examining the behavior of the table-based model
against a foundry transistor model