This 1 kHz circuit was found in American documentation from the 90s. The original operational amplifier consists of a double 741 at the time. The power supply must be symmetrical.
The output power of this wireless intercom for the 27 MHz (11 meters) range is in the order of ½ W,...
This circuit was published in an Italian magazine Radio Elettronica in February 1976. The...
This circuit for very low current measurements was found in an American 80's documentation. The used...