Found in Motorola documentation from the 1970s, the circuit presented uses a component from the era that is not common today. The characteristics of the coils are given next to the diagram.
The operational amplifier is a type introduced at the time by RCA. The circuit is from a Radio...
Found in a 1967 documentation this circuit can be applied to any operational amplifier. Components...
This RCA commercial radio had its circuit published in Radio Electronics magazine in August 1959....