This circuit provides 2.5 W of power with 6 V supply and 4-ohm speaker. We found it in the Radio Electronics magazine of April 1990.
This power source, obtained in a 1973 publication, suggests the use of partially burned germanium...
This circuit was obtained from an Electronic Design from 1964. Transistors admit modern...
The circuit is from the 1994 National Semiconductor Linear Applications Handbook but can be...