Three Phase Mixed-mode CMOS VCO with Grounded Passive Components

The design of sinusoidal oscillators has been an active area of research in the field of analog electronics. Particularly, oscillators capable of providing waveforms in phase quadrature and circuits capable of generating multip le phase oscillat ing voltage and/or current waveforms are of interest fro m the viewpoint of their applicat ions in communication systems. In this paper, a mixed-mode three phase sinusoidal oscillator, emp loying Second Generation Dual-X Current Conveyor as the active build ing block and grounded passive elements, is p resented. A feedback scheme consisting of three cascaded inverting first-order low-pass sections is employed to obtain a three phase voltage-mode as well as current-mode sinusoidal signals simultaneously. The condition of oscillations and the frequency oscillations are independently controllable. The proposed circuits are co mpatible with CMOS integration by virtue of the fact that only M OSFETs and grounded capacitors are utilized. Circuit simu lations using PSPICE yielded pro mising results in the form of excellent matching between the theoretical and simulated values. Variation of the frequency of oscillation with the capacitor value is exp lored. Electronic control of the frequency of oscillat ion by means of a control voltage is also demonstrated.