This configuration makes use of currently uncommon components. In fact, we found it in documentation from the 70s. Equivalent operational amplifiers can be used.
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...