Using the 741 this basic circuit was found in the November 1973 Radio Electronics magazine. The power supply must be symmetrical. The components can be recalculated for other frequencies.
This fader or guitar fading circuit was found in an American documentation from the 1980s. The...
Found in 90's Electronic Engineering this circuit can be used to measure phase angles between two...
This circuit, from Motorola 1976 documentation, uses a common field effect transistor at the time....