This circuit with a bargraph scale was found in a 90s Popular Electronics. The circuit measures the intensity of a sound in three scales. R14 works as a sensitivity adjustment.
This circuit was found in the October 1989 issue of Radio Electronics magazine. It drives an...
This interesting configuration was found in a 1965s Electronic Design. It makes use of components of...
This interesting bandpass filter using an operational amplifier 741 has its cutoff frequency...