Low-sensitivity SAB band-pass active-RC filter using impedance tapering

The design procedure of low-sensitivity second-and third-order class-4 Sallen and Key active resistance-capacitance (RC) allpole filters, using impedance tapering, has already been published. There a ladder structure in the positive feedback loop of an operational amplifier was used. In this paper desensitization using impedance tapering is applied to class-3 circuits with negative feedback referred to as a "single-amplifier biquad" (SAB). The RC-section in the negative feedback loop is impedance scaled upwards from the driving source to the negative amplifier input. Second-order band-pass filters are considered. The improvement comes free of charge: component count and topology remain unchanged, whereas the component values. Selected for impedance tapering, account for the significant decrease in sensitivity to component tolerances.