This circuit was suggested by General Electric in a 1969 documentation. The transistors are of the time and the power supply is not given. Note the high supply voltage.
This simple photometer uses a 1 mA milliammeter and a common phototransistor. The circuit has its...
The circuit of the figure allows to implement a multimeter of high sensitivity or even to use a...
This simple circuit must be powered by a voltage of 5 V. The integrated circuit is the 7400, but...