Wien bridge oscillator circuit

The feedback network of the Wien bridge oscillator uses an RC series-parallel frequency selection network.
The phase shift of the circuit at Xiu-1/RC is zero, so in order to form positive feedback,
a non-inverting amplifier must be used. Usually it can be composed of a two-stage common emitter circuit,
or a non-inverting integrated operational amplifier VA747. The oscillation circuit composed of the latter
is shown in Figure 21-33 and is called a Wien bridge oscillator.
    1) The integrated operational amplifier is vA747.
    2) The values ​​of resistor R and capacitor C are determined by the oscillation frequency of the oscillator.
    The Wien bridge oscillator shown in the figure is used as a variable frequency oscillator
in the frequency range from a few hertz to several hundred kilohertz . Its frequency adjustable range is much larger than that of the LC oscillation circuit, and it is easy to adjust.     When the signal frequency input to the RC network is crucian carp. =1/RC, the maximum feedback coefficient is F=l/3, and Uf is in the same phase as the output voltage U. As long as the voltage amplification factor of the non-inverting amplifier A>3, a sine wave with frequency ‰=1/RC can be generated. The non-inverting amplifier is composed of an operational amplifier , and its voltage amplification factor is much greater than 3. In order to control the amplification factor, it also plays a role in improving the oscillation waveform and stabilizing the amplitude. In the circuit , in addition to the RC frequency selection network that plays a positive feedback role . A negative feedback circuit with deep feedback and automatic adjustment feedback function is also introduced, which is composed of Ri and Crown.