I see DC bias characteristics for ceramic capacitor where capacitance decreases with applied voltage. I am not finding the same data for electrolytic capacitors. Do electrolytic capacitor values vary like ceramic capacitors with applied voltage?
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4 Answers
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Capacitance variation with DC bias for aluminum electrolytic capacitors is insignificant. The following graph is a 3300 uF, 63 V Nichicon aluminum electrolytic capacitor. Data is from a HP4194A impedance analyzer. Over the 20 V span, the capacitance change is less than 0.7%. Data was taken at 1 kHz.
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Two additional graphs are added as the slight capacitance change with voltage is intriguing. One is a smaller aluminum electrolytic, the other is an aluminum polymer. Both show more percentage capacitance change versus bias voltage than the 3300uF capacitor.
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1\$\begingroup\$ +1 for providing actual, measured results \$\endgroup\$– zebonautCommented Jan 30 at 11:48
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\$\begingroup\$ Nice to see some quantified results. How long did that measurement take? I assume the voltage slope had to be pretty slow to avoid affecting the results. \$\endgroup\$ Commented Jan 30 at 15:36
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1\$\begingroup\$ @SpehroPefhany 200 points took about one minute (felt like forever). Had to sweep slow so the capacitor charging would keep step with the measurement which meant putting the analyzer on long integration time. An interesting question since I've never bothered to investigate this. \$\endgroup\$– qrkCommented Jan 31 at 0:48
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\$\begingroup\$ @qrk Yes, interesting. I wonder what mechanism causes the capacitance to increase with voltage. The electric field across the oxide layer is very strong (in V/m). \$\endgroup\$ Commented Jan 31 at 2:40
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No. Capacitance variation with DC bias only occurs to any significant extent in type-II ceramic dielectrics.
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No, electrolytic capacitors are stable with DC bias, as are ceramic caps with COG (NPO) dielectrics, and film capacitors. Ceramic capacitors with type II dielectrics are the commonly used capacitors that have DC bias derating.
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Electrolytic capacitors can show some voltage dependence, but it is generally less significant compared to ceramic capacitors.
Here is another thread that you can take a look at:
Capacitors: voltage-dependent capacitance? Electrolytic Capacitors can filter out clutter or interference waves in the circuit, so they are also called smooth filter capacitors. Here is a pretty cool article about capacitor symbols. It may help you while working with different types of capacitors: https://www.jakelectronics.com/blog/a-guide-to-understand-capacitor-symbols
