This circuit for light modulated in frequency (FM) operating at 50 kHz was found in a 90’s Electronics Now. The circuit has an active filter. Modern equivalent transistors can be used.
This low drift or offset circuit is from an 80's documentation. The configuration can be made with...
This circuit has a logarithmic response as a function of the light falling on the sensor. The...
Found in 80's Electronic Engineering, this circuit can tune the frequency to be rejected. The power...