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Phototransistor Vs. Photodiode

Discussion in 'General Electronics Discussion' started by RaevenCogan, Mar 17, 2011.

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  1. RaevenCogan


    Mar 13, 2011
    :eek: Hey guys, I was wondering what is the difference in function between the two?
  2. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    Jan 21, 2010
    One is a transistor, the other is a diode.

    A photodiode can be operated in a number of modes, but essentially photons striking the junction allow a single electron to move across the junction.

    photons striking the base junction of a phototransistor are amplified by the transistor action allowing a much higher number of electrons to travel between collector and emitter.

    So you will see greater absolute changes in current if you use a phototransistor.

    A photodiode may have a much faster response though (important if you need nanosecond -- or faster -- response)
  3. RaevenCogan


    Mar 13, 2011
    Thanks Steve :)
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