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November 01, 2025, 09:45:10 am
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Author Topic: photodiode  (Read 645 times)  Share 

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Shark 774

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photodiode
« on: May 19, 2011, 10:31:22 am »
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The current through a reverse biased photodiode can be measured and then looking at the graph we can find the lux. However, could we find the potential difference across a FORWARD biased photodiode and from the graph also work out the lux??
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schnappy

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Re: photodiode
« Reply #1 on: May 19, 2011, 01:36:54 pm »
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Diodes are non-ohmic, so the voltage across the diode is constant. It won't tell you anything other than the reverse bias voltage across the diode!
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Shark 774

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Re: photodiode
« Reply #2 on: May 19, 2011, 10:37:04 pm »
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Quote from: schnappy on May 19, 2011, 01:36:54 pm
Diodes are non-ohmic, so the voltage across the diode is constant. It won't tell you anything other than the reverse bias voltage across the diode!

If you look at the graph of the characteristics of a photodiode, the voltage actually increases as the lux increases. However I don't think that it's sensitive enough to the change in lux, where as the change in current when reversed biased is very sensitive to the lux.
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