We found this circuit in a Japanese publication in 1967. The circuit consists of a 15 W audio amplifier with germanium transistors including a voltage indicator power supply.
This basic configuration of voltage regulator using operational amplifier and zener was found in a...
This circuit was obtained in a 90’s Popular Electronics. The frequency depends on C1, a component...
We found this circuit in the 1990 Radio Electronics Special Projects magazine. The circuit has a...