With this circuit it is possible to obtain a higher voltage from a zener diode. The circuit is from a 1970’s EEE. The device used as a constant current source is uncommon today.
The circuit shown is from an old European publication. In it we have the way to activate a relay...
We found this circuit in a European publication from the 1990s. Transistors are still common types...
This circuit was found in an American documentation and can be added to common amplifiers of any...