Some observations on single-element control sine-wave oscillators

A new generalized approach to the study of the variable frequency sine-wave oscillators in active RC filters having a single-element control facility is presented. The constraints on the filter functions which are amenable for generation of such oscillations with feedback are derived and a number of exemplary circuits are given and also their frequency and gain limits in tables. The oscillation stability is also studied following Loeb's criterion of limit cycle stability for systems having saturation characteristics in the active parts. The circuits are also shown to yield VCO's with voltage controlled FET as the frequency controlling parameter, The possible configurations of the amplifier circuits with operational amplifiers as the building block are considered including a discussion on bandwidth limitation.