This adjustable circuit from 0 to 200 nA was found in a 90's EDN. The components can still be found relatively easily, as they are CMOS.
This proximity relay circuit was found in the July 1990 Radio Electronics magazine. The supply...
This sensitive circuit for triggering relays was found in an old English publication. It works with...
This circuit was obtained from a 90’s Linear Technology documentation. The circuit provides...