Cascade switched-capacitor IIR decimating filters

Comprehensive methodologies are described for the design of infinite impulse response switched-capacitor (SC) decimating filters employing either externally cascaded or internally cascaded structures. The former are more appropriate to achieve high decimating factors but suffer from the effects of unwanted aliasing frequency components associated with the intermediate sampling frequencies. The latter overcome this problem but become more complex to design to attain high decimating factors. Such decimating filters allow not only to relax the requirements of continuous-time pre-filters in the context of traditional SC filter systems but also to realize arbitrary baseband and anti-aliasing amplitude responses employing operational amplifiers with more relaxed speed requirements than their traditional SC filters counterparts. Examples are given to illustrate the proposed methodologies