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Monday, August 8, 2016

Application Note 113 - DC and AC Voltage Dependence of Ceramic Capacitors


Ceramic materials most commonly utilized for the manufacture of multilayer capacitors are either defined as being Class I dielectrics, which are considered to be very stable in nature, or Class II dielectrics, which in comparison, have higher dielectric constants and dissipation factor values and are considered less stable in nature. Class I dielectrics like NPO (COG) and negative coefficient materials, exhibit a linear relationship of polarization when exposed to an electric field and the resulting effect on dielectric constant and/or dielectric loss is considered to be negligible. Class II dielectrics like X7R, X5R, X5U and Z5U on the other hand, are comprised of ferroelectric materials and as such, they exhibit a non-linear polarization response when exposed to an electric field. This nonlinear response can not only change the dielectric constant of the capacitor, it can also under AC bias, result in an increase in dissipation factor and subsequent self-heating of the capacitor. Understanding how the capacitor might behave when operated under both DC and AC bias is very important in ensuring proper capacitor selection and long term reliability of the device.

The remainder of AN113 can be located on the Application Page along with other Application Notes and our Theory Notes.

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