Realizations of IIR/FIR and N-path filters using a novel switched-capacitor technique

Two canonical and two ladder structures are proposed for the realization of infinite impulse response (IIR) transfer functions using switched-capacitor (SC) differentiators and the synthetic division technique. The resultant filter structures are simple, compact, and stray insensitive. They have a low component sensitivity, good low-frequency noise performance, and adequate dynamic range. Theoretical calculation and SWITCAP simulation results on certain types of filters show good consistency with the experimental results, substantiating both design methodology and circuit functions. Circuit examples are given and their functions are successfully verified through chip fabrication and measurement. The multiplexed SC differentiators are modified to form three types of N-path circuits which can be used to design a narrowband bandpass filter. Because the N-path circuits are based upon SC differentiators rather than SC integrators, they have distinct performance superior to that of SC integrator-based N-path circuits