Electronically Tunable Resistorless Mixed Mode Biquad Filters

This paper presents a new realization of electronically tunable mixed mode (including transadmittance-and voltage-modes) biquad filter with single input, three outputs or three inputs, single output using voltage differencing transconductance amplifier (VDTA), a recently introduced active element. It can simultaneously realize standard filtering signals: low-pass, band-pass and high-pass or by selecting input terminals, it can realize all five different filtering signals: low-pass, band-pass, high-pass, band-stop and all-pass. The proposed filter circuit offers the following attractive feature: no requirement of inverting type input signal which is require no addition circuit, critical component matching conditions are not required in the design, the circuit parameters coo and Q can be set orthogonally or independently through adjusting the bias currents of the VDTAs, the proposed circuit employs two active and minimum numbers of passive components. Furthermore, this filter was investigated from the point of view of limited frequency range, stability conditions, effects of parasitic elements and effects of non-ideal and sensitivity. Thus, taking these effects and conditions into consideration, working conditions and boundaries of this filter are determined. We also performed Monte Carlo, THD and noise analyses. Simulation results are given to confirm theoretical analyses.