I found interesting article about capacitance of ceramic capacitors may depend on voltage applied.

It seems to be that in some designs you can face a problem when ceramic capacitor capacitance may strongly depend on voltage. Few tests were done with various capacitors using following circuit:

In the circuit C_X – tested capacitor; C_{0 –} known capacitor. Voltage vas regulated from 0 to 50V using potentiometer R1. 50V is taken as nominal voltage of ceramic capacitor. Because Two capacitors are connected in series the total capacitance is C=C_X·C₀/(C_X+C₀) then we find capacitance of tested capacitor C_X=C·C₀/(C₀-C); C₀ – is about 10 % of C_X value.

There were several capacitors tested and stunning results were found. - Some of capacitors lost capacitance from 10 to 15 times due to increase of voltage up to 50V. Even when 10% of voltage were applied the capacitance was only about 35 – 40% of nominal value.

One and only explanation may be that low quality dielectric material is used in (no-name) ceramic capacitors. Of course not all capacitors gave following results. But be ready for this when using unknown producer ceramic capacitors.

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This entry was posted on Tuesday, January 9th, 2007 at 6:45 pm and is filed under Electronics. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.