Low Sensitivity Coupled CMOS CCII Biquads

In this paper we examine the influence of coupling to reduce the sensitivity to component tolerances in a CMOS-CCII realization of a fourth-order band-pass filter using two two-integrator biquads: cascaded and coupled. It is shown how the CCII non-idealities, causing lossy integrators, influence the coupled biquad design. With the example of a fourth-order 1MHz/100kHz band-pass filter, the design is tested with post-layout simulations with AMS 0.35-micron technology using Cadence. The analysis of the performance of both filters is done with Cadence. It is demonstrated that the coupled biquads, although having one more CCII and a resistor, have significantly lower sensitivity to component tolerances than the equivalent biquad cascade.