|MadSci Network: Physics|
Thank you for the question. A standard diode has a current - voltage characteristic such that current flows relatively easily in one direction (+V) and very poorly in the other direction (-V). The only significant difference a photodiode makes is that its current or voltage is effected by the amount of light with energy greater than or equal to energy gap of the diode junction. So the voltage (if you do something to hold current constant) or more typically the current (if you hold the voltage at some constant 0 V to some negative voltage - called reverse bias condition) varies continuously as a function of the photons (quanta of light, of infrared energy in your question) being absorbed. The only problem which arises is when one applies a voltage equal to or greater than the "breakdown voltage". At that point the diode starts to draw excessive current which dwarfs any photovoltaic effect. http://en.wikipedia.org/wiki/Photodiode http://www.rp-photonics.com/photodiodes.html
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