| An accurate mathematical method for computing the output spectrum of a linear time-invariant periodically switched network in steady state is described. Beyond the exponential inputs of earlier works, the described method is expanded to include a square wave. This addition allows the output spectrum, due to clock voltages, to be studied for the first time. This clock noise is often the limiting factor in switched-capacitor filter noise performance.;Models are developed for integrated FET switches, both MOS and JFET, and operational amplifiers which, when used in the previously described analysis technique and computer program, provide excellent correlation to laboratory results.;A clarification of the output spectrum of a switched network due to offset voltage at either the filter input or at the operational amplifier is provided. This offset analysis is compared to both simulation results and actual laboratory data.;Also for the first time, it is shown that the output spectrum of circuits with no hold at the input is subject to switch ON resistance. This dependance is clearly seen in the transfer function of switched-capacitor bandpass filters.;A computer program has been written (listing provided) to solve the developed matrix equations for the output spectrum of such a network. The program inputs are simply a state space description of the network in each of the two clock periods. |
