This circuit is from an old American documentation and its use in motorcycles with 12 V is suggested to power 6V radios. The transistor can be the BD136 and BC548.
The LM339 is a voltage comparator, but it can be used as a low frequency amplifier, as shown in...
This circuit was found in a 1966 publication using a microwave transistor of the time. The circuit...
This circuit was found in a 2005 Linear Technology application manual. The circuit is for 48 V...