Impedance tapering effects on "low-Q" SAB band-pass active-RC filter,” IWISPA 2000

AbstractThe design procedure of low-sensitivity active resistance-capacitance (RC) allpole filters, using impedance tapering, has already been published. The low-sensitivity filter sections already described in publication are class 4 (TT-SABB) Sallen and Key sections. In this paper class 3 (SAB) sections for low pole-Q realization are considered. Impedance tapering is applied on L-sections, which are situated in negative-feedback of operational amplifier in open-loop mode. L-sections are impedance scaled upwards, from the driving source to the negative amplifier input. Second-order band-pass filter is considered. Pole-Q factors for low-Q building blocks take their values up to, say, 5. The sensitivity to component tolerances of the circuit is shown to be small for any type of impedance tapering regardless of the gain-sensitivity product (GSP) value. Index TermsAllpole filters, biquadratic active filters, class 3 active filters for low-Q realization, low-sensitivity active filters. 1