Amplitude control in a triangular wave quadrature oscillator

The simple circuits that have been usually reported as triangular wave quadrature generators are based on conservative equations that do not properly describe the starting transient and the amplitude stabilization mechanism. As has been shown in a previous work, the slew-rate of the operational amplifier and the limited output voltage of the integrator are responsible for the starting and the stabilization of the generated waveforms. As an extension of this work, in this communication, a new simple circuit for generating triangular waves in quadrature is proposed. This circuit allows both obtaining the correct quadrature between the triangular waves and controlling their amplitude. This amplitude control is accomplished by the variation of a relation between resistors, thus allowing electronic control. Simulation results show good agreement with theoretical predictions