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

I-V characteristics of a diode

  1. Sep 17, 2016 #1
    I was doing an experiment to plot the IV characteristics of a diode. I connected a resistor, diode and milli ammeter in series. I connected a voltmeter across the diode. I measured the diode voltage and diode current. When i changed the resistor, I got a different set of diode voltage readings for the corresponding diode current. Why are the readings different?

    Before I changed the resistor, i waited for 15 mins to allow the diode to cool back to normal temperature. The ammeter resistance is 0 and voltmeter resistance is infinite.
     
  2. jcsd
  3. Sep 17, 2016 #2

    Averagesupernova

    User Avatar
    Science Advisor
    Gold Member

    Interesting. I would think they would be the same. Are you sure you weren't comparing 50 mA to 500 mA or something? Could be easy to do depending on your meter.
     
  4. Sep 17, 2016 #3

    Merlin3189

    User Avatar
    Gold Member

    Well there's one factor, because your ammeter will not be zero resistance and your voltmeter will not be infinite. You'd like them to be, but they can't be perfect. *
    Typically an electronic voltmeter is about 10MΩ and your milliammeter maybe 1Ω.

    Without knowing the details of what size resistors and what meters you were using, it's hard to say whether this was the cause of your error. Perhaps you could give details? What diode, what meters, what voltage supply, what range of currents you tested and which test gave you the problematic results.

    Edit: * Unless you mean you are using simulation software, rather than doing a real experiment!
     
  5. Sep 18, 2016 #4

    tech99

    User Avatar
    Gold Member

    I wonder if your circuit connections are correct. It sounds as if you are measuring voltage across the resistor rather than across the diode.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted