This circuit is an improvement over the previous one, using the same capacitor system as a sensor. We also found it in Radio Electronics from the 80s.
This small earphone amplifier with germanium transistors was obtained in a Japanese publication from...
The sensor for this circuit is a phototransistor. We found it in the April 1971 issue of Radio...
Found in a 90s Popular Electronics, this circuit allows to select the operating ranges between...