This circuit operates from 20 Hz to over 20 kHz and is easily tunable. We found it in a 70s documentation. The circuit can be implemented with modern operational amplifiers.
This voltage regulator was obtained in the SGS manual of linear integrated circuits of 1982. The...
Of course, the design indicates a specific application for a touch switch. Thus, analyzing the...
In the figure we have the way to obtain the Exclusive-OR function with 1 transistor. The circuit...