New Electronically Tunable Low-frequency Quadrature Oscillator Using Operational Transresistance Amplifier

This paper describes, a new realization of electronically tunable low-frequency quadrature sinusoidal oscillator (LFSO) based on Operational transresistance amplifier (OTRA). The proposed structure employs two OTRAs, along with four resistors and three capacitors. The notable properties of the proposed oscillator are: (1) it bares independent controllability of frequency of oscillation (FO) through resistors without altering the condition of oscillation (CO) and vice versa; (2) suitable for MOS-C realization making FO electronically tunable (3) exhibits low passive sensitivities (4) enjoys good frequency stability properties. Besides, the roots of the characteristic equation are evaluated to calculate the condition for startup oscillations, which results in altering the property of uncoupling tuning between CO and FO to orthogonal tuning. Furthermore, the nonideal behaviour of proposed LFSO has been examined using single pole model of the OTRA. The proposed LFSO was simulated using Spectre in Cadence employing generic Process Design Kit (GPDK) 0.18 mu m CMOS process. The post-layout, schematic-driven simulation results obtained agree firmly with the theoretical formulations. The total harmonic distortion (THD) is found to be below 3%.