A four-inputs single-output current-mode biquad filter using a minimum number of active and passive components

This article presents a four-inputs single output biquadratic filter performing completely standard functions: low-pass, high-pass, band-pass, band-reject and all-pass functions, based on single current controlled current follower transconductance amplifier (CCCFTA). The features of the circuit are that; the quality factor and natural frequency can be tuned electronically via the input bias current; the circuit description is very simple, consisting of merely 1 CCCFTA and 2 grounded capacitors; the filter does not require inverting-type input current signal. Additionally, each function response can be selected by suitably selecting input signals with digital method. Using only single active element and grounded capacitors, the proposed circuit is very suitable to further develop into an integrated circuit. The PSPICE simulation results are depicted. The given results agree well with the theoretical anticipation.