Analytical and Experimental Approaches for the Design of Low-Distortion Wien Bridge Oscillators

Although Wien bridge oscillators are commonly used as fixed-frequency generators of low distortion there has apparently not been suggested a simple systematic method based on nonlinear theory for reducing their distortions. The present paper attempts at filling this gap. This is achieved by suggesting a network which is on one hand a Wien bridge oscillator and it can be also regarded as a van der Pol oscillator. Van der Pol oscillators, however, are well known and as a result the task of systematically reducing the distortion becomes a straightforward procedure which is demonstrated by a series of experiments. Additional improvements (in the economy of design and with regard to a further reduction of distortions) are attained by slightly modifying the basic van der Pol type system. The small level of distortion achieved in the present work systems is explained in the conclusions section as partly due to the deliberate generation of harmonic components which are then subtracted from the output signal to remove the distortion components which are added by the amplifier circuit.