Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Capacitance of a forward biased diode

  1. Jan 29, 2010 #1
    How does a forward biased p-n junction display capacitive effect? I understand that a reverse biased diode can exhibit capacitance with the depletion region acting as a dielectric, but in a forward biased junction, depletion region does not exist,so how does it show capacitive behaviour?
     
  2. jcsd
  3. Jan 30, 2010 #2
    I may be wrong because I don't know a lot about the physics of semiconductors, but a sentence on the wikipedia description of a forward biased diode struck me as relevant to your question.

    Ok, when the diode is forward biased, current still doesn't flow, right. So there is a potential difference between each part of the diode, like in a capacitor. In addition it says on the wikipedia page that "This reduces the width of the depletion zone.".

    So it seems to me that as long as the foward bias is not too large, there is still a depletion zone between the N and P parts, and there is a potential difference across it. So it should have some capacitive properties, right?

    Ref:
    http://en.wikipedia.org/wiki/P-n_junction#Forward_bias

    Torquil
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook