Nooby diode question

Discussion in 'General Electronics Chat' started by impaJah, Aug 5, 2012.

  1. impaJah

    Thread Starter New Member

    Aug 2, 2012
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    If I were to reverse bias a regular PN diode, would a current be generated for a split second on the N-type silicon side as it dumps it's excess electrons to the positive terminal?
     
  2. MrChips

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    Oct 2, 2009
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    Maybe, but that is the wrong effect. A reverse biased semiconductor diode becomes a capacitor. What you should see is the charge flow (albeit very small) as the capacitor charges up.
     
  3. impaJah

    Thread Starter New Member

    Aug 2, 2012
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    Oh I left out an important part of this thought experiment! Let's say you ONLY connect the N-type silicon to ground, without connecting the P-type side to a negative terminal. Would a small current be generated then do you think?
     
  4. MrChips

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  5. impaJah

    Thread Starter New Member

    Aug 2, 2012
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    No, my question's a little different. I'm wondering if electrons will move from the N-type part of the diode (not to it) and to the positive terminal or ground when reverse biased. This would only be for a split second and I'm wondering this because the N-type silicon is doped with an element that naturally has extra electrons.
     
  6. MrChips

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    The doping process adds impurities such as phosphorous to silicon to create N-type semiconductor. There are extra valence electrons but these are not free electrons, i.e. the N-type material is still neutral in charge.

    When the N-type is bonded to the P-type material which has the ability to accept an extra electron, there is an instant flow of electrons from the N-type to the P-type. The resultant electric field created prevents more electrons from migrating.

    The net charge is still zero.
     
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  7. crutschow

    Expert

    Mar 14, 2008
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    A normal silicon junction diode does generate a short reverse current when the bias is changed from forward to reverse due to the minority charge carriers stored in the junction depletion region. Schottky diodes are an exception to this and do not have a significant reverse current since they are majority carrier devices and have no minority charge carriers at the junction.
     
  8. WBahn

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    Mar 31, 2012
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    If you are leaving the P side dangling, then how are you reverse biasing it?

    If you talking about taking a diode that is sitting on a desk and then connecting the N side to a supply terminal, then there is no reason for current to flow at all. You have merely defined a reference voltage for both terminals.
     
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  9. radiohead

    Active Member

    May 28, 2009
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    are you trying to use a diode as a battery? Even if the n-type material were to generate a current when connected, it would be so tiny that it would be an insignificant power source.
     
  10. WBahn

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    Mar 31, 2012
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    No, I believe he's trying to just do a thought experiment to get his mind around how things work in a p-n junction.
     
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  11. impaJah

    Thread Starter New Member

    Aug 2, 2012
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    I did some research on valence electrons and I think I understand things better. Thanks!!!!!!!
     
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