RC phase-shifter variable sinusoidal oscillators using initial conditions-restoration amplitude control

A low-distortion instrumentation-quality variable sinusoidal oscillator using RC phase-shifters with the initial conditions-restoration amplitude control technique is developed. The variable frequency range is greater than five orders of magnitude. An exact analysis of the oscillation and the distortion characteristics, including the effects of the restoration time, the nonunity loop-gain, and the tuning component mismatchings upon the oscillator amplitude and the distortion is presented. The discrete-time simulation technique has been used to investigate the oscillation dynamics when the frequency is continuously changing. Experimental results confirming the validity of the theory and the high performance obtainable in practice are also presented. The basic idea of the oscillator is applied to a range of very-low-cost commercial signal generators