This simple low current circuit was found in a Radio Electronics magazine from August 1960. The circuit does not use transistors in regulation, but only zeners directly.
This circuit is from an old manual of operational amplifiers. The setting can be adapted to work...
The operational amplifiers used on this Motorola circuit from the 1970s are no longer common, but...
This circuit uses a feedback system that latches the relay when closed. The circuit uses an...