This circuit multiplies the input voltage by 3 and can work with up to 12 V input. The current is a few mA. We found it in the Radio Electronics magazine of December 1992.
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...