A Wien bridge RC oscillator with fast amplitude control

The paper describes fast amplitude control in a Wien bridge RC oscillator. This fast control is achieved restoring ( within each period) a node voltage in the passive RC two-port of positive feedback. As a result the new value of the output voltage amplitude can be established with the delay which is not more than one oscillation period. The total harmonic distortion ( THD) is calculated and the condition of low distortion is established. The low-THD oscillator includes the circuit for damping-ratio control as well. The experimental data show that THD below 0-1% is achieved.