This 1980s documentation circuit uses a 741 in a different high-speed comparator configuration. The feed must be symmetrical. The diode is general-purpose.
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...