With the help of a circuit diagram show that photodiode can be used to convert light signals into electrical signals.

Asked by Thomas Albin | 10th Jan, 2013, 01:50: PM

Expert Answer:


If placed in a dark room, the photodiode is exposed to no light; therefore it creates no electricity. However, if light falls upon it, it takes the light energy and produces electric current in response.

A photodiode conducts electric current directly proportional to the amount of light that falls upon it. It's a perfect direct relationship.
A photodiode operates in a circuit in reverse bias. This means that the anode connects to ground of the circuit and the cathode connects to the positive voltage supply of the circuit. Current flows from the cathode to the anode when exposed to sufficient light.
The amount of light that a photodiode can pick up and, thus, the amount of current that it produces depends mostly on the surface area of the photodiode. The larger the surface area, the more light that it can pick up; and thus the more current it produces. One tradeoff of more current production is the larger size. More space must be accomodoated for a circuit design to accomodate the greater space. Another tradeoff of the larger surface area is that response time slows down. The circuit tends to produce current more slowly in response to the light when the surface area is larger. When the surface area is small, response time is quicker and the circuit can have high-speed responses.
more thorough circuit:

Answered by  | 10th Jan, 2013, 03:03: PM

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