Gregory explains the circuit of a Wien Bridge Oscillator, that uses automatic gain control and a PLL architecture for amplitude and frequency stability.
The Wien bridge oscillator works by positive feedback excitation over a linear amplifier. Very high harmonic purity is accomplished by the passive feedback network and the linear operation.
Automatic gain control is need to sustain oscillation at a constant amplitude, preventing saturation or suppression of the signal.
The frequency stability of a normal Wien bridge oscillator is defined by the phase-slope of the feedback network. For this design, the desired output phase-noise improvement was accomplished by locking the linear oscillator in a PLL architecture.
Watch the video showing the circuit working:
https://youtu.be/LU8pOYLmtxo
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