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

Abstract

Using novel SC (switched-capacitor) differentiators and the synthetic division technique, discrete-time IIR and FIR (infinite- and finite-impulse-response) transfer functions have been realized by sample-data SC analog circuits. The resulting filter structures are simple, compact, and stray-insensitive. Moreover, they have a low component sensitivity, good low-frequency noise performance, and large enough dynamic range. Theoretical calculation and SWITCAP simulation results on certain types of filters have shown good consistency with the experimental results, which substantiates both the design methodology and the circuit functions. The multiplexing technique can be directly applied to the SC differentiators without modification. Thus the multiplex differentiators can be used to design filter banks, which may save chip area and reduce DC power dissipation. 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 on SC differentiators rather than SC integrators, they have a distinct performance superiority to SC integrator-based N-path circuits. >