Using an LDR as a sensor, this circuit is from the Radio Electronics magazine of December 1984. The operational amplifier is the 741 and the source must be symmetrical.
This is a typical symmetrical power supply configuration. The transformer voltage determines the...
This stereo meter-indicator was found in the August 1971 issue of Radio Electronics magazine. The...
This circuit was found in an American documentation from 1970. We can increase the number of...