This high-impedance headphone circuit was found in a 1990s William Sheets. The power is low, but the high input impedance makes it useful for radio applications.
This traditional crystal radio circuit, but which has a modern version with diode, was found in an...
This circuit, obtained from a 1989 publication, can control motors up to 1.5 A. With the LM350 this...
Using the CK722 this directional photometer was published in Radio Electronics magazine in July...