Analysis and Optimization of SFDR in Differential Active-RC Filters

This paper presents a method for optimizing SFDR in differential active-RC filters. Simple analytical expressions for noise and third-order intermodulation (IM3) distortion in active-RC filters are derived. The nonlinear behavior of two-stage Miller-compensated op amps, which are extensively used in active-RC implementations, is also modeled. These expressions and models are used to maximize SFDR in active-RC filters by means of proper admittance scaling and optimizing the share of each op amp in the total power consumption. It is shown that both the power consumption of the filter and its area can be significantly reduced, for a given SFDR, by exploiting the presented method.