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 circuit is recommended for alarm systems since it has a good output stage. The circuit is...
) Suggested by Philips in a 1968 documentation this circuit has very high 10 ohm on-load voltage...
No information is given about the transformers in this circuit suggested by Motorola in a 1968...