Capacitor Selection: Beyond Capacitance Values
Selecting a capacitor requires more than matching the Farad value. Voltage rating, Equivalent Series Resistance (ESR), and dielectric absorption are critical.
Class II ceramic capacitors (like X7R and Y5V) exhibit significant DC bias effects. A 10µF 6.3V Y5V capacitor may lose 80% of its effective capacitance when biased at 5V, according to Murata's 2021 characterization data.
Key Specifications Data
| Dielectric | Stability | DC Bias Effect | ESR |
|---|---|---|---|
| C0G/NP0 | Excellent | None | Very Low |
| X7R | Moderate | Moderate | Low |
| Y5V | Poor | Severe | Low |
| Alum. Electrolytic | Poor (Temp dependent) | None | High |
Frequently Asked Questions
Why is my voltage rail oscillating?
High ESR in output filter capacitors can cause regulator instability. Check the datasheet for required minimum and maximum ESR.
Can I replace an electrolytic with a ceramic?
Yes, but due to the lower ESR of ceramics, linear voltage regulators might become unstable. Always check the regulator's stability curve.
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