Current-mode universal biquad with orthogonal ωo-Q tuning using OTAs

A two-input two-output (TITO) current-mode universal biquad using only four dual-output operational transconductance amplifier (DO-OTAs) and two grounded capacitors is described. By appropriately connecting the input and output terminals, the proposed circuit can provide lowpass, bandpass, highpass, bandstop and allpass current responses. The filter also offers an independent electronic control of the natural frequency (omega_o) and the quality factor (Q) through the transconductance gain (g_m) of the DO-OTAs. No critical matching conditions are imposed for realizing all the filter responses, and all the incremental parameter sensitivities are low.