The FETs of this circuit can be the BF245. The circuit is from an old documentation and can be used in the amplification of infrasonic waves, of a sonic attack, for example.
This two-transistor amplifier can be used as power stage for intercom, experimental receivers,...
This sensitive circuit was found in old English documentation. Transistors may be modern...
This configuration, already presented in other points of this section and website, is of a...