Voltage-mode low-pass, high-pass, band-pass biquad filter using simple CMOS OTAs

A high input impedance electronically tunable voltage-mode biquadratic filter with single input and three outputs using four simple CMOS operational transconductance amplifiers and two grounded capacitors is proposed. The proposed filter provides low-pass, band-pass and high-pass voltage responses at a high input impedance terminal, which enables easy cascadability of the voltage circuit. Also, the parameters ω_o and Q can be set orthogonally by adjusting the circuit components. For the realizing of all the filter responses, no critical matching condition is required, on inverting-type input signal is imposed and all the incremental parameter sensitivities are low. The performances of the proposed circuit are simulated with PSPICE to confirm the presented theory. The band-stop and all-pass responses can also be obtained by interconnection of relevant output voltages with summer circuits.