Found in documentation from the 1990s, this circuit converts 12 V to 9 V from a car's power output. The 100mA current eliminates the need for a heatsink on the transistor.
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...