Power consumption versus filter topology in SC filters

One of the major problems in biomedical and other signal processing circuit designs is the reduction of power consumption. If the amplifiers of a switched-capacitor (SC) filter are coupled together in one of the clock phases, then they have much higher gain-bandwidth requirements than in an uncoupled configuration. This results in a more than proportional increase in power consumption. Two formalisms are discussed, which lead to analytical derivations of minimal amplifier requirements. In the first, one of the amplifiers in the circuit is isolated. Formulas are derived for the loop gain around that amplifier, as the form of the loop gain T(s) determines total charge transfer inaccuracy errors. The other one formalism considers the matrix representation presented by E. Sanchez-Sinencio et al. (1984). Here, it is shown that coupling integrating amplifiers in a loop, leads to very inefficient use of the bandwidth of the amplifiers, and hence to excess power consumption.