MMCC based electronically tunable allpass filters using grounded synthetic inductor

Abstract

New circuit implementations of electronically tunable first and second order allpass filter (AP) structures using a Multiplication Mode Current Conveyor (MMCC) building block are presented. The control voltage (V) of the MMCC tunes the desired phase (θ) while the time constant (τ) is adjustable by a Differential Voltage Current Conveyor Transconductance Amplifier (DVCCTA)-based synthetic lossless grounded inductor (L). The circuits are analyzed taking into account the device imperfections which show low active sensitivity features of the designs. The effects of port transfer error (ε) and that of the parasitic capacitances of the active devices had been meticulously examined which indicated that certain deviations in nominal design equations occur; these however, could be minimized with appropriate choice of the circuit passive components. Readily available AD-844 type Current Feedback Amplifier (CFA) elements are utilized for the topology implementation. Satisfactory test results on electronic θ-tunability, upto about 300 KHz, had been verified by PSPICE simulation and with hardware experimentation.