This circuit was found in Raytheon's 1967 documentation. The circuit uses an operating of the era, but the configuration can be applied to modern operational amplifiers.
We found this crystal AM radio using a germanium diode in a Japanese magazine in 1967. The circuit...
This filter was found in Radio Electronics, and its configuration can be applied to any...
This circuit was obtained in an old English magazine (TSI) 1998 and consists of a Schmitt trigger...