We found this circuit in the Radio Electronics magazine of May 1977. The circuit has the frequency given by the components according to the formula next to the diagram.
We found this circuit in a 1975 publication. The circuit can be made with more modern equivalent...
August 2016 - It can be obtained from Mouser Electronics the power factor controller NCP1602 from...
This is a traditional circuit in which a 741 operational amplifier is used as an audio amplifier with...