Noise analysis of switched capacitor networks

Noise generated in switched capacitor (SC) networks has its origin in the thermal fluctuations of charged particles in the channels of the MOS switch transistors on one hand, in the operational amplifiers on the other hand. Using a SC integrator as vehicle, it is shown that the output noise spectrum consists in general of a broad-band component due to a continuous-time noise signal and of a narrow-band contribution predominating in the baseband of the SC network resulting from a sampled-data noise signal. The ratio of undersampling is introduced and it is shown that the latter noise contribution can be evaluated by sampled-data techniques using the
z
-transform transfer function. These results are applied to the SC integrator and excellent concordance to the measurements made on a laboratory model is established.