Realization of Cochlear Model by VLT Switched-Capacitor Filter Biquads

Abstract

We describe here the realization of a cochlear model using switched capacitor filters (SCF). This approach is made possible by a new design technique, called charge differencing (CD), which reduces by up to 50% the silicon area required to implement very large time-constant (VLT) filter biquads. In this technique, filter time constants are controlled by ratios of capacitor differences making the capacitor spread ratio very small. The new SCF's are also parasitics-free and are stabilized against op-amp inaccuracies, such as input offsets and finite gains, using a two-phase gain-offset-compensation method.