We found this circuit in an old publication. The components used are rare today. Accuracy depends on the resistors in the input selection network. The circuit operates from 10 to 500 kHz.
This circuit for frequencies up to a few tens of megahertz was found in the April 1978 issue of...
This is another possible version of a negative voltage generator using a 555 integrated circuit. The...
This Dimmer circuit for incandescent lamps was found in an English documentation. The input...