This commercial circuit is from a Japanese magazine from 1967. It uses germanium transistors, and the coil can be made with 80 to 100 turns of fine enameled wire on a ferrite rod.
This circuit was obtained in a 1979 101 Electronics Projects. The circuit can be assembled easily,...
Suggested by a 90's Linear Databook, this circuit compensates for capacitor hysteresis. The main...
This circuit serves to isolate analog signals, for example, audio signals in a secure link...