This circuit provides a 5 V negative voltage from a positive input voltage. Found in old American documentation, information on the used integrated circuit was not provided. Probably an oscillator.
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...