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.
This circuit was found in Motorola documentation from the 1980s. PUTs are not common components...
This low distortion circuit was found in a 1964 Electronic Design. The transistor admits...
This circuit is based on an uncommon Texas component today, as found in an American 1980s...