This article presents two circuits of mixed-mode quadrature oscillator based-on voltage differencing transconductance amplifier (VDTA). The circuits consist of two VDTAs and two grounded capacitors. The quadrature outputs both voltage-mode and current-mode are studied. The high-impedance output current, which is connected easily to load or next stages circuit and the amplitude can be electronically adjusted with the dc bias current. In addition, the grounded capacitors were well-done for integral circuits (IC) implementation. The condition of oscillation (CO) and frequency of oscillation (FO) can be electronically/orthogonally controlled by tuning the dc bias currents. The results of PSPICE simulation are accordant with the theoretical analysis. Moreover, the proposed circuit can operate at very low voltage of ± 1.25 V and only 1.33 mW of power dissipation.

Keywords: Quadrature oscillator, Voltage differencing transconductance amplifier (VDTA), Grounded capacitor