This circuit for audio signals was found in the March 1990 Radio Electronics magazine. The circuit uses a unusual optocoupler that can be replaced with an equivalent one.
This circuit from an old documentation uses an optocoupler to control the feedback. FET is...
We found this circuit in a publication for radio amateurs in 1974. The bipolar transistors can be...
This circuit was found in a documentation for radio amateurs from the 70s. The integrated circuits...