Two-amplifier active-RC biquads with minimized dependence on op-amp parameters

It is generally recognized that the best two-amplifier active- biquads show a better performance with lower sensitivities than single-amplifier biquads (SAB\´s), and that the performance of an SAB can be improved by use of a composite amplifier. In this paper it is demonstrated that by matching the characteristics of a composite amplifier to the specific filter\´s requirements a "composite single-amplifier biquad" (CAB) can be obtained with significantly better performance than that of the best two-amplifier biquads reported to date. The resulting circuits are shown by theory and experiment to belong to the best available active- filters.