ImDrovements in the Theory arid Design
Br Ian L. Stevens, Richard P. Manning · 1971
HE PROPERTIES most commonly required of the output waveform of a sinusoidal oscillator are good frequency stability, low harmonic content, and good amplitude stability. These properties are interrelated and dependent on both the amplifier and the frequency selective network used in the oscillator. This paper studies the frequency stability of RC oscillators. Frequency stability is improved by providing “impedance isolation” between the frequency selective network and the maintaining amplifier, and by using frequency selective networks with large values of the “stability factor” S. Good impedance isolation requires large values of the “isolation factor” I. It is shown that the requirements of a large isolation factor and a large stability factor are conflicting. The superiority of bridge oscillators over single-loop oscillators is established in terms of the stability factor. The common RC networks are then optimized in terms of maximum S for a given degree of impedance isolation. This leads to some new. constraints on the networks and to a new procedure for choosing an oscillator network.