This 1970 Electronic Design circuit uses a varactor or varicap. The circuit divides the frequency of a 150 MHz signal by 2. Similar versions appear on this site.
This circuit was found in the Electronics Experimenter Handbook from 1991. The sensor is a diode...
This circuit can be used on audio, video, or data links to receive modulated infrared signals. The gain is...
With this circuit it is possible to obtain a voltage modulated in amplitude with a maximum current of...