Measurement and Modeling of Nonlinear Components for Spice Simulation of Signal Distortions by Protection Circuits

Nonlinear protection circuits which protect vulnerable circuits from fast powerful transients distort also the signals. This problem complicates the protection circuit design. To avoid an expensive trial-and-error-design of these circuits, simulation models of nonlinear components such as varistors and Z-diodes for SPICE have been created [1], This paper describes the models and a way to obtain their parameters from a practical point of view. It is also useful for those who use software different from SPICE. In SPICE the circuit can be simulated with these models simply by typing a net list and starting a simulation. A way to investigate nonlinear effects is a transient analysis with a sinusoidal input followed by a Fourier analysis. The name SPICE is used as a generic term for [1] and for derived commercial products. The methods described here may also be applied to other nonlinear RF circuits, e.g. mixers.