All electronic circuits are nonlinear: this is a fundamental truth of electronic engineering. The linear assumption that underlies most modern circuit theory is in practice only an approximation. Some circuits, such as small-signal amplifiers, are only very weakly nonlinear, however, and are used in systems as if they were linear. Other circuits, such as frequency multipliers, exploit the nonlinearities in their circuit elements; these circuits would not be possible if nonlinearities did not exist. It is absolutely clear that designing nonlinear circuits is more complicated than linear ones. Nonlinear Designs require many issues such as nonlinear circuit elements models and simulation which both of them are going to be discussed in this thesis. In this thesis we first examine the effects of nonlinearity and How to analyze nonlinear circuits. Then modeling of semiconductor devices is discussed and the relations between these models are extracted. We study Harmonic Balance method and show how this analysis works. Volterra Series method is discussed in separate chapter as the main method in this thesis and ways of obtaining nonlinear transfer function used in this method are extracted. We use the semiconductor models to develop the nonlinearities in a bipolar transistor structure. We use the optimum Volterra series method to extract the terms related to intermodulation distortion according to the transistor nonlinearities, considering temperature as a parameter and separating the origins of these nonlinearities. Although our results are based on firm mathematical basis, we used Matlab and compare numerical results of our equations which were obtained by implementing a GUI program in Matlab with numerical results of Microwave Office.
