Comments on "Design techniques for improved capacitor area efficiency in switched-capacitor biquads" by H. Quiting and W. Sansen

In the above-titled paper (see ibid., vol.CAS-34, p.1590-9, 1987) a method for calculating the capacitance ratio constraint for optimal dynamic range is developed. The authors point out that the mathematical derivation of the capacitance ratio constraint for optimal dynamic range is a formidable task. They employ a set of simplifications, which leads to results that are only applicable for special filter types and parameters. The commenters report that if the derivation is carried out, results that are valid for the general case are obtained after some pages of algebra. They give the solutions and demonstrate the usefulness of their general analysis by means of an example, the E-filter, from the paper.<>