The output power spectrum produced by correlated double sampling

Correlated double sampling (CDS) provides an excellent method for the reduction of kTC noise in analog signal processing. The authors derive the CDS output power for two-circuit realizations of the double sampling procedure. One realization employs two MOSFET switches while the other replaces one switch with a delay element. Although the methods are not identical in function, they both produce equivalent output power spectra. For arbitrary input power, the output exhibits aliasing in multiples of the frequency with which the switch (switches) of the CDS circuit closes (close). White noise on the input, therefore, may lead to large low-frequency output spectrum values if the system bandwidth is appreciable. The general results are used to derive of both the power spectrum and its integral for the special case of an input signal of first-order low-pass filtered white noise. The authors plot the output power spectrum for two typical cases in which the input may be described as the combination of a (white) Johnson noise and 1/f noise. A comparison of this effort with previously reported research is given