This circuit was found in a 90s EDN. Its purpose is to increase the efficiency of operational amplifiers. Power MOSFETs and inverted zeners support equivalents.
The integrated circuit used in this project is not common today, but it can be implemented with more...
Found in an American publication from 1969, this circuit can be adapted to be used as a shield....
This current meter with many scales was found in a 80s American documentation. The operational amplifier...