Electronically controlled high input and low output impedance voltage mode multifunction filter with grounded capacitors

In this study, a three-input single-output voltage-mode biquadratic filter employing voltage differencing differential input buffered amplifier (VD-DIBA) is presented. The proposed filter uses two VD-DIBAs and two grounded capacitors without any external resistors, which is well suited for integrated circuit implementation. The circuit provides five standard transfer functions, namely, low pass, high pass, band pass, notch and all pass filters with electronic control of quality factor and pole frequency. Each transfer function can be selected by suitably selecting input signals via digital method. The filter does not require inverting of the input voltage signal. Moreover, the circuit possesses high input and low output impedances and thus it enables simple voltage-mode cascading. The PSPICE simulation and also experimental results are included, verifying the workability of the proposed filter. The given results agree well with the theoretical anticipation.