This circuit detects when an audio signal exceeds a certain level or even occurs due to an object falling, a door slamming or other. The circuit is from a Radio Electronics from January 1980.
This two-phase stepper motor circuit was found in an old documentation using an operational amplifier...
This circuit is suggested by National Semiconductor and with two operational amplifiers an LM833...
This circuit is from the September 1985 issue of Radio Electronics magazine. The circuit has an...