4. Imperfections due to active elements

The performance of a switched-capacitor filter depends critically on the quality of its components. Capacitors must be in precise, stable ratios, with only low-value parasitic capacitances. Amplifiers need to transfer charge as quickly as possible, which implies a short settling time and a very fast rise time. They must have a low offset voltage. Switches must have very low forward resistances and low parasitic capacitances. Finally, and most importantly, amplifiers must generate low noise and be able to reject external noise, especially from the power supply.

A detailed study of these various imperfections and the means used by manufacturers to remedy them is beyond the scope of this article. The interested reader may wish to consult the excellent review article by J. Allstot and W. Black [10] ....