Thermal noise is one of the most important challenges in
analogue integrated 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 low-distortion delta sigma converter.