This PLL circuit was found in the April 1978 issue of Radio Electronics magazine. The circuit is powered with up to 15 V voltages from a symmetrical source.
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...