Active rc single-opamp design of driving-point impedances

The active RC simulation of LC filters is of interest, due to the excellent sensitivity properties thereby obtained. Most known designs of active RC driving-point impedances necessary for the simulation of an LC filter, require two opamps per impedance. In this paper a method is presented that realizes general second-order driving-point impedances with only one opamp and with a minimum number of capacitors and resistors. The method is based upon an interesting property of active RC driving-point impedances which is derived in the paper. This property relates the well-known properties of driving-point impedance poles and zeros to the zeros of the feedback voltage-transfer functions in a single-opamp second-order filter structure.