Electronics Applications - 0 views
www.asc.vic.edu.au/...cations%20of%20electronics.htm
4star diode electronics ldr led photodiode sensor
shared by York Jong on 30 May 07
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The current through a photodiode is directly proportional to the light intensity
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The photodiode and phototransistor can be both photovoltaic (generators of potential difference) and photoconductive (modifiers of an electric current), depending on the application.
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A reverse-biased photodiode operates in what is called photoconductive mode, since the conduction of the semiconductor junction varies with the illuminating light intensity. If the reverse-biased voltage is relatively large (i.e. several volts) the reverse-biased photodiode will have a very fast response time (much faster than an LDR) and is suitable for detecting light signals that vary down to a time scale of a fraction of a microsecond.
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When light shines on the LDR, it has low resistance and allows current to flow. When light does not shine on it, the LDR has a very high resistance, and a much smaller current will not flow through it.