In the figure we have the typical circuit of a stereo decoder using the TBA450N integrated circuit. The circuit is from the 1976 Siemens manual. No information was given on the coils.
This circuit can also use other series operational amplifiers such as MC33172, MC33174, MC35171,...
Found in Popular Electronics from the 90s, this circuit mutes a scanner's speaker in the absence of a...
This circuit was found in General Electric documentation from 1965. The transistors are from that...