This unusual circuit from a Popular Electronics of the 90s uses LED indicators, operating as a bridge. The components used are common. It is based on the tuning of the signal by a PLL.
This circuit was found in a Radio Electronics issue from May 1989. Please note that it may not...
We found this circuit in an English magazine from 1976. The magazine no longer exists, but just...
Texas Instruments' low power operational amplifiers OPAx196 can be found on Mouser Electronics....