Light and Light Communications
1. Phototransistor Receiver Module
It’s easy to squeeze miniaturized LED transistors and phototransistor receivers into 16-pin DIP modules with the help of 8-pin MINIDIP ICs. Figure A is a photo of an infrared transmitter and receiver assembled in this fashion.
Fig. A Miniature IR modules
Figure B is a circuit diagram for the receiver. In operation, photons impinging upon the phototransistor cause a small photocurrent to flow. This signal is passed by C1 to the 741 op amp which has a gain (determined by R2 and R3) of 1000. The amplified signal appears at pin 6 of the 741 where it can be coupled to another ...
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