This LM380-based circuit was found in documentation from the 1980s. The components are current, and the transistor may be a general-purpose equivalent. Note the use of a medium impedance speaker.
This circuit can be used in bridge of sensitive measures. We found it in a documentation from the...
This interface was found in a Modern Electronics magazine from 1990. Although the circuit is...
Found in an old American documentation, this step has as input and output transformers coupling. Two...