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 was found in the National Semiconductor's Linear Applications of 1978. The circuit uses...
Indicated for checking the operation of small FM transmitters, this circuit was found in an...
We found this circuit in Radio Electronics magazine from September 1959. The circuit has different...