Realization of cochlear filters by VLT switched capacitor biquads

The realization of cochlear filters using switched capacitor biquads is described. This approach is made possible by a new design technique, called charge-differencing (CD), which easily reduces by 25% (or more) the silicon area required to implement very-large-time-constant (VLT) biquads. In this technique, filter time constants are controlled by both the product of two capacitor ratios and the differences of capacitor values, making the capacitor spread ratio very small. The new switched capacitor biquads are also stabilized against operational-amplifier nonideal characteristics, such as input offsets and finite gains, using a two-phase gain- and offset-compensation method