AGC Wien Bridge Oscillator

It stabilises on 1.1Vrms shake or briefly click the switch. This thing acts very weird, i mean logically following how it works. First without the stabilization feedback the oscillator doesn't work (the wave fades), because the 500k and 100nF RC filter reinforces the gain provided by the 9.9k and 1uF filter. So the amplitude starts growing, and at a given point the extra gain provided by the 500k/100nF starts to fall, slowly, at some point reaching equilibrium thus stabilizing the output. So it works in the beginning as a PTC (at which point it adds ro the gain) and later on becomes an NTC (substracting from the gain)

published 10 years ago