An approach is presented for the analysis of the nonlinearnbehavior of analog integrated circuits. The approach is based on anvariant of the Volterra series approach for frequency domain analysis ofnweakly nonlinear circuits with one input port, such as amplifiers, andnwith more than one input port, such as analog mixers and multipliers. Byncoupling numerical results with symbolic results, both obtained withnthis method, insight into the nonlinear operation of analog integratedncircuits can be gained. For accurate distortion computations, thenaccuracy of the transistor models is critical. A MOS transistor model isndiscussed that allows us to explain the measured fourth-order nonlinearnbehavior of a 1 GHz CMOS upconverter. Further, the method is illustratednwith several examples, including the analysis of an operationalnamplifier up to its gain-bandwidth product. This example has also beennverified experimentally
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