This Wien bridge oscillator circuit uses a Texas Instruments 709 amplifier. It was found in an article in the September 1972 issue of Radio Electronics magazine. It is powered by a 24 V voltage.
This circuit appears elsewhere on this site, but from different sources. Using the LM3900, we find this...
This interesting source or isolation transformer also allows to vary the output voltage by...
In this circuit the CA3140, an operational amplifier, is used as a comparator with the zener diode...