Wide-range oscillator with digital control for digital waveform generation

A variable frequency oscillator with precise digital control over a very wide frequency range has been developed. Two standard VCO chips are used to form two independent phase-locked loops; one adjusted to cover the lower frequency range and the other the higher frequency range. A simple decoder circuit selects the output from the appropriate VCO and also ensures a smooth crossover in the intermediate frequency range. The output is synchronised with a low frequency reference input and is ideally suited for use as a clock in variable frequency digital sinewave generation circuits.