This circuit was found in a National Semiconductor manual from the 1980s. The operational amplifier is from that time and the waveforms are shown in the diagram.
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...