Abstract
A generalized feedback oscillator consisting of an ideal nonlinear amplifier and a linear, passive or active LMCR network is considered. The network is of second order and has a โbiquadraticโ voltage transfer function.
Though such a system represents a large family of important oscillators, it appears that an explicit nonlinear differential equation for it is not known. Consequently, a general nonlinear differential equation, valid for all possible secondโorder oscillators is derived. This contains explicitly all the network and amplifier parameters. The van der Pol equation is shown to be a special case of the general equation and to represent the simplest secondโorder oscillator. Transient and steadyโstate solutions of the general equation are obtained for the case of nearly sinusoidal oscillations. The solutions provide explicit expressions for the transient rise time, steadyโstate amplitude, harmonic content and the frequency instability of the oscillator output waveform. The expressions can be used to analyse and evaluate all possible types of secondโorder oscillators. A figure of merit for the oscillator network is defined, and the conditions to be met by the amplifier and the network in order to produce oscillations are determined. Validity of the formulas is verified experimentally by means of two representative oscillators.