This step of good gain was obtained in an American publication of the 1980s. The circuit can be powered by voltages from 3 to 9 V and the FET can be of almost any type.
This photo-relay uses a Darlington stage to increase sensivity. Any photo-transistor can be used....
This circuit has a logarithmic response as a function of the light falling on the sensor. The...
This circuit is used to test capacitors with a working voltage above 150 V, detecting shorts or...