Current-mode multiple-feedback filters

A different class of operational-amplifier-based biquadratic filters, the infinite-gain multiple-feedback filters, is transformed into its current version. This class has so far eluded any such transformation because the operational-amplifier is configured without resistive feedback loop. The current-mode multiple-feedback filters contain also a single operational-amplifier as the active element, and therefore an absolute comparison between voltage and current versions is feasible. The authors demonstrate, both theoretically and practically, that the current-mode multiple-feedback filters can extend the useful bandwidth with respect to their classical voltage-mode counterparts up to nearly the GB product of the operational-amplifier. This result is particularly interesting because voltage- and current-mode multiple-feedback filters contain exactly the same active and passive components