The circuit shown is from a 1994 National Semiconductor documentation and can be implemented with more modern operational amplifiers. The power supply must be symmetrical.
This circuit with a bargraph scale was found in a 90s Popular Electronics. The circuit measures...
This grid-dip meter was found in a 1956 documentation from Sylvania. It can be implemented with...
This power source takes advantage of an old valve transformer that is no longer used and can...