Wien Bridge Oscillator (Potentiometer Gain Adjust)

Wien Bridge sine wave oscillator for amplitude limiting, gain adjustment is through a potentiometer. The op-amp in the circuit is not ideal but a virtual model. Although the circuit does not have a power supply the Positive voltage swing (Vomp) and Negative voltage swing (Vomn) are parameters that make the output bounded so the circuit oscillates as expected. "Initial conditions" is set to "User defined". "Initial voltage" (IC) for Cfsp is enabled. If set near ≈ 3.875 V the initial amplitude of oscillation is almost equal to the stable level. Values of "Initial voltage" (IC) for Cfsp in the millivolts and lower range result to oscillation that grows in amplitude and stabilizes when the voltage swing limit of the op-amp is reached. Lower "Initial voltage" (IC) for Cfsp results to longer stabilization time. "Manual time step" is enabled and "Time step" is set to the default value of 1e-5 s to make the graph smoother. With the feedback resistor and diodes shorted out, an ideal gain of 3 will be obtained with the wiper of the potentiometer set at 33.33 %. With the feedback resistor and diodes in the circuit, the potentiometer is set to 35 % (slightly higher than the ideal). The sum of the feedback resistance and the 65 % remaining resistance of the potentiometer sets the initial gain slightly higher than 3. As the magnitude of the output voltage grows and a diode starts to be forward-biased, the gain decreases stabilizing and smoothing the oscillatory signal. Decreasing the wiper setting of the potentiometer increases the distortion. f = 1,061,032.9539459689051258917558168 Hz