This is the commercial circuit for the TRF-44 amplifier sold in Japan in the 1960s. The circuit provides a few hundred milliwatts and is intended to be used as small, battery-powered turntables.
The operational amplifier used on this 1968 circuit is not common today. However, the setting can be...
This configuration reaches a few tens of megahertz depending on the crystal and the FET....
This optically coupled circuit was found in the February 1968 Radio Electronics magazine. The...