Multiphase sinusoidal oscillator using inverting-mode operational amplifiers

This paper describes a simple multiphase sinusoidal oscillator based on inverting operational amplifiers (OPAs). The system comprises n cascaded inverting first-order low-pass stages and produces n odd-phase equal amplitude signals that are equally spaced in phase, from low-impedance sources. The basic scheme utilizes self-oscillation and can produce 2n even-phase signals by the inclusion of n unity gain inverters. A modified system employing signal injection through the associated phase-shifting network is also discussed. The negative feedback around the OPA's results in extremely good frequency and distortion performances that are unmatched by other multiphase system implementations. Moreover, the system has a large output voltage swing, high current drive capacity, and utilizes readily available components.