Gain-bandwidth product effects on SC filters including a quasi-optimal topology

The gain-bandwidth product (GB) effects on switched-capacitor (SC) filters are analyzed and described in detail. A systematic general analysis method is reviewed. To biquad SC filters with the same ideal transfer function are compared. It is shown that when the op amps are modeled with one dominant pole, their frequency responses differ significantly. The importance of switch phasing is emphasized and explained, and GB effects on SC filters are discussed. A quasi-optimal SC biquad topology with respect to GB effects is described. Its performance is illustrated by means of a root-locus plot. This plot allows the designer to determine the ω
₀
and
Q
deviations for different values of GB/ω
₀
.