Three-input one-output voltage-mode universal filter using simple OTAs

This paper presents three-input one-output voltage-mode electronically tunable universal filter using only simple CMOS operational transconductance amplifiers. The proposed filter provides low-pass, band-pass, high-pass, band-stop and allpass filters into one single topology. For realize all the filtering function, no component-matching conditions are required. The natural frequency and the quality factor can be controlled orthogonally and electronically by adjusting the bias currents. The proposed filter is simulated using PSPICE simulators to confirm the presented theory.