Talk:Photodiode
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Hi there. Can someone please put some stuff up for the construcion and how th photo diodes work please?
What are some possible reasons photodiodes do not reach saturation?
I think that this article needs to mention semiconductor physics or link to a discussion therein. Therobotbuilder 19:57, 12 November 2006 (UTC)
I have some conservation of energy angst. The diode's built-in field is what accelerates the electrons to create the drift velocity (hence current) in the diode. So the energy that is generated from a photovoltaic cell would seem to come from the p-n junction (and its' charge carrier gradient), not the light source which generated the electron-hole pair in the first place. I know the light must be the source of energy behind the current that is generated, but I can't quite see how. can anyone explain? Andybuckle 16:48, 15 January 2007 (UTC)
"electrons that are generated by photons in the base-collector junction _are injected into the base_" in the description of phototransistor work in the first para. Is that true? Aren't the electrons swept into the collector, increasing its current and the holes gather in the base region increasing its voltage? --Janislaw 10:35, 16 January 2007 (UTC)
Picture
Can Someone confirm that the pictures is actually a photodiode. It looks like an LED. 194.200.145.5 13:24, 2 February 2007 (UTC)
An LED can serve as a photodiode. In fact, every diode is photosensitive. --Phil Roan, 71.116.81.130 (talk) 00:15, 24 December 2007 (UTC)
[edit] Reverse Bias
The article states that reverse-biasing "strengthens the photocurrent". Does this refer to some minor effect, or is it just false? If you're getting only one electron per photon, the current will be set by the photon rate and be independent of applied voltage. Also, I'm not familiar with the effects of "expanding the reaction volume". Is that going to create better efficiency? I thought the only reason to reverse-bias a photodiode was to reduce the capacitance, thereby increasing the response speed. Spiel496 15:54, 24 May 2007 (UTC)
Spiel is correct. Reverse bias does not strengthen the photocurrent (For a visual see the graph at [1]). In fact, the article has it backwards. Reverse bias causes photocurrent, decreasing the sensitivity of the device. However, it significantly lowers the capacitance, which causes improvements in the response time because the time constant is a product of the load resistance with the junction capacitance. --Phil Roan, 71.116.81.130 (talk) 00:15, 24 December 2007 (UTC)
Picture of square device looks exactly like a solar battery I have from an LCD power supply. Much different in that it creates electron flow versus controls electron flow. Now about that gain in a phototransistor.
[edit] Graphs or schematics
It might help to add a graph with I-V curves under different levels of illumination or a schematic for an equivalent circuit, e.g. current source (dependent on light level) in parallel with a regular diode and possibly some resistors or capacitors Nrnkpeukdzr (talk) 04:20, 13 January 2008 (UTC)
