Current-mode universal filter and quadrature oscillator using current controlled current follower transconductance amplifiers

This paper presents a new current-mode quadrature oscillator and universal filter that employs two current controlled current follower transconductance amplifiers and two grounded capacitors. The proposed circuit can be realized either as a quadrature oscillator or as a universal filter without changing circuit topology. In case the circuit works as a quadrature oscillator, the condition and the frequency of oscillation can be independently and electronically controlled. Four-phase quadrature current outputs and two-phase quadrature voltage outputs can also be obtained. In case the circuit works as a universal filter, low-pass, high-pass, band-pass, band-stop and all-pass filtering functions can be obtained simultaneously by appropriately selecting the input and output signals. The natural frequency and the quality factor of filter can also be obtained independently and electronically. PSPICE simulation results are used to verify the workability of the new topology.