This circuit is from a Radio Electronics from February 1959. The circuit has a speaker output and good sensitivity. Power is supplied from a 9 V battery.
The recommended distance between the emitter and the phototransistor is 10 mm for this...
The input and output frequencies of this circuit depend on the coils and capacitors of the tuned...
This circuit was obtained in a 1991 publication. What it does is to amplify a signal with unit...