This circuit is from the Linear Applications Handbook of the National Semiconductor of 1994. Transistors are common, but the integrated circuit is not easy to obtain 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...