Comparison of a class of active filters with respect to the operational-amplifier gain-bandwidth product

Abstracr-A class of positive-feedback active RC filters which realize high stable Q´s is presented. This class generalizes the earlier circuits of Tarmy and Ghausi and of Moschytz. The performance of the circuits presented is analyzed using a one-pole rolloff model for the operational amplifier. The Q and wO variations due to one-pole rolloff are tabulated for different filters. It is shown that the positive-feedback filters have lower Q sensitivity to the gain-bandwidth product than the state-variable filter. The theoretical behavior of the circuit Q is experimentally verified.