If you have the skills and can get your hands on SMD components, you can assemble this small amplifier. We found it in the Radio Electronics Experimenter special edition from 1990.
This circuit was found in a 1992 publication. The circuit uses common components and includes the...
This protection circuit for battery chargers was found in an old Elektor. The relay is according to...
This very low frequency amplifier has a gain of 1,000 and was found in a 1967 documentation. The circuit is...