This circuit is from a 1980s Signetics documentation. The circuit separates the modulation signal from a carrier. The used components are not common today.
This conventional window comparator configuration was found in an old documentation. It is valid...
We found this configuration in a Radio Shack documentation from 1977. Here we have the way to...
This is a single transistor stage for a phototransistor. The circuit is suggested by Texas...