The purpose of this circuit is to check the linearity of SSB amplifiers. The circuit was found in an old documentation for hams. The diode is a general purpose detector type.
The integrated circuit used in this application is not very common. The circuit is intended for...
The focused circuit was found in the National Semiconductor's Linear Applications Handbook of...
The TDA2040 is not a common IC these days, but if you find one you can build this high quality...