This high sensitivity circuit was found in the July 1992 Radio Electronics magazine. The circuit drives a buzzer, but a relay can be used to activate an external load.
Found in an Electronic Design from the 90s, this circuit does not need sinks for its components. The...
The figure shows a way to apply gain control to the LM3600 OTA. The circuit is from a Radio...
This circuit was found in a 1968’s General Electric documentation. The circuit has a control range of...