This circuit, from a component manual, also applies to other components in the same family. The font does not have to be symmetrical, and the characteristics are given next to the diagram.
The phototransistor can be of any type and the adjustment potentiometer 4M7. This circuit was...
We found this circuit in a Popular Electronics from the 90s. Its purpose is to monitor a power...
This configuration can be made based on other operational amplifiers. For other frequencies, the...