This circuit was found in a Popular Electronics of the 90s. The operational amplifier admits equivalent and the phototransistor can be of any type.
This circuit with transistors was found in an old Japanese publication, translation of an American...
This 8 W amplifier with germanium transistors was found in a Japanese documentation from 1967. The...
This circuit of the 80's makes use of components of the time. The circuit is from an American...