REALIZATIONS OF IIR FIR AND N-PATH FILTERS USING A NOVEL SWITCHED-CAPACITOR TECHNIQUE

Applying novel SC differentiators and the synthetic division technique, discrete-time IIR and FIR transfer functions have been realized by sample-data SC analog circuits. The resultant 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 design methodology and circuit functions. 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 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 upon SC differentiators rather than SC integrators, they have distinct performance superior to that of SC integrator-based N-path circuits. © 1990 IEEE