A multifrequency technique for frequency response computation with application to switched-capacitor circuits with nonlinearities

Frequency domain analysis of switched-capacitor and other clocked circuits including nonlinearities is a difficult problem requiring special attention. Conventional nonlinear frequency response methods are computationally intensive and time consuming for circuits with large transient components. In this paper, we present a novel technique for the rapid estimation of the nonlinear frequency response of switched-capacitor circuits. The analysis technique is formulated using a multifrequency sinusoidal excitation to drive the circuit into its steady-state condition. Then, the fundamental components are extracted using a frequency-directed Discrete Fourier Transform (DFT) in order to construct the frequency response. The key steps of this approach include the selection of noninterfering input frequencies and the determination of properly scaled input amplitudes. In addition, a method is proposed to reach steady-state quickly and to detect the steady-state condition for use in conjunction with the multifrequency approach described here.