Suggested by Siliconix in documentation from the 90s, this amplifier has its gain digitally selected. The components are from that time, not easy to find 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...