What Is a Polymer Capacitor?
A polymer capacitor is a modern capacitor that uses a solid conductive polymer instead of a liquid electrolyte. Its biggest advantage is very low ESR and long life.
Operation
The solid polymer electrolyte removes the problem of a liquid electrolyte drying out; so the capacitor is more stable and longer-lived.
Difference From Electrolytic/Tantalum
| Property | Polymer | Liquid electrolytic |
|---|---|---|
| ESR | Very low | High |
| Lifetime | Long | Limited (dries out) |
| Cost | High | Low |
Advantages
Thanks to low ESR it carries high ripple current with little heating; it responds fast and improves efficiency. It's common on computer motherboards.
Where Is It Used?
Processor power lines, graphics cards, high-current DC-DC outputs and anywhere low ESR is needed.
Limitations and Hybrid Polymer
Polymer capacitors usually work in a lower voltage and capacitance range than liquid electrolytics. To close this gap, hybrid types combining liquid and solid polymer have been developed; these offer both low ESR and higher voltage withstand, combining the advantages of both.
Common Mistakes
- Ignoring cost: using polymer where it isn't needed is needlessly expensive.
- Skipping the voltage margin: a suitable voltage margin should be left with polymer too.
- Swapping one-for-one with liquid electrolytic: the ESR difference can change the circuit's behavior.
Frequently Asked Questions
Why is a polymer capacitor preferred?+
Does it swell?+
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