LED operates as light sensor

Posted on Nov 11, 2012

Using a simple 741 amplifier connected as a current-to-voltage converter with the LED as the current source, the voltage at the output is proportional to incident light. The junction is Q biased only by the difference between the output summing node junction potential and ground, preventing the possibility of reverse breakdown. The photon-generated current equals the short-circuit current of the junction, which is linearly related to incident light.

LED operates as light sensor
Click here to download the full size of the above Circuit.

The sensor requires a level of incident illumination that depends on the degree of opacity of the LED Fig. 51-5 package.

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