We found this circuit in a Popular Electronics from the 90s. It operates at a frequency of 15 kHz. Components can be difficult to obtain, such as the integrated circuit.
This amplifier from 100 to 150mW was found in a Japanese documentation from 1967. The circuit uses...
This circuit is from a manual of JFETs and can be implemented with the BF245 and for the bipolar...
This source of some amps for voltages up to 40 V was found in an Italian magazine Elettronica...