OPTIMIZING TWO COMMONLY USED ACTIVE-FILTER BUILDING BLOCKS USING THE COMPLEMENTARY TRANSFORMATION.

In the paper, the minimization of the gain-sensitivity product (g. s. p. ) for two important active-filter types that are finding widespread use in voiceband communication systems, in the form of hybrid-integrated filter building blocks, is considered. The first comprises a twin I for zero realization: this is incorporated in the positive-feedback loop of a single operational amplifier and is referred to as the twin-T s. a. b. b. The known conditions for minimum g. s. p. for the twin-T s. a. b. b. are briefly recapitulated and expanded. The second comprises a differential scheme for zero realization, and combines positive and negative feedback. It is referred to as the single-amplifier biquad (s. a. b. ). The paper shows that the two circuits are closely related by the complementary transformation, and that conditions for minimum g. s. p. in both cases are identical.