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Capacitance Decrease w/ Applied DC

  1. Apr 28, 2005 #1
    I would like to understand why my 100uF 6.3V X5R dielectric ceramic capacitor decreases to ~60uF under a 5V applied DC bias. Can anyone explain the physical phenomenon?
     
  2. jcsd
  3. Apr 28, 2005 #2
    So, you applied 5V to 100uF cap and when you measured its capacitance by some equipment after removing supply it was 60uF. Am I right? Did you measured the capacitance at other voltages too?
     
  4. Apr 28, 2005 #3
    Remember that capacitance is a constant and can't be changed normally if the capacitor is being used under the working voltage mentioned for that component.
     
  5. Apr 28, 2005 #4
    The decrease in capacitance is while the 5V DC is applied. I can measure the capacitance at 60uF with an applied DC voltage. When I remove the 5V supply (DC Bias = 0V), the measured capacitance goes up to 80uF, which is just barely above the lower limit for the 100uF cap (+/-20%).

    The capacitance is not constant! It's a well known phenomenon that some dielectrics decrease in permitivity as a function of an applied DC voltage, or an increase/decrease in temperature, etc. I just wanted to understand the phenomenon.
     
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