In this circuit the voltage across the LED is limited by the diodes. The maximum current also depends on the resistor.
This circuit was found on a Radio Electronics of July 1984. It consists of a source with the 741...
This receiver for an audio link by modulated light was found in a 90s Elektor. Transistors are common...
We found this circuit in a Radio Electronics from October 1963. The circuit uses an output...