THERMAL NOISE ANALYSIS OF SWITCHED CAPACITOR NETWORKS

Abstract

Thermal noise is one of the most important challenges in analogue intergrated circuits design. This problem is more critical in switched capacitor (Sc) filters due to the aliasing effect of wide band thermal noise. In these circuits, switching introduces a boost in the power spectral density of the thermal noise due to aliasing. Unfortunately, even though the theory of noise in Sc circuits is discussed in the literature, it is very tedious and requires highly sophisticated and not widely available software. The purpose of this paper is twofold. It provides a tutorial description of the physical phenomena taking place in anSc circuit while it processes noise. It also proposes some specialized but highly efficient algorithms for estimating the resulting sampled noise in Sc circuits, which need only simple calculations. A practical design procedure, which follows directly from the estimate, is also described. The accuracy of the proposed estimation algorithms is verified by simulation using spectre RF. As an example, it is applied to the estimation of the total thermal noise in a second order lowdistortion delta sigma converter.