This precision reference circuit was found in documentation from the 1980s. It applies to other operational amplifiers. The power supply must be symmetrical.
The circuit below shows how to use an LM139 comparator or series equivalent as an amplifier. The...
We found this receiver circuit for modulated light in a 90s Popular Electronics. Equivalent audio...
The circuit was found in the February 1992 Radio Electronics magazine. The scale can be changed by...