This circuit was found in a 90s Popular Electronics. With it, using a 4066, it is possible to control between 1 to 100 the gain of an operational amplifier like the 741.
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...