This balance or balance circuit with phase inversion was found in documentation from the 90s. Transistors can be low noise equivalents like BC549.
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...