This circuit synchronized by the power grid can be used as a shield. We found it in an 80's Electronic Engineering. R1 can typically be 4k7.
The L293 circuit is not common today. We found this circuit in the 1982 SGS linear integrated...
We found this bridge circuit in Electronics Now magazine from September 1995. The instrument can...
We found this divider in a circuit manual from the 90s. The circuit is intended for operation with...