Reference sheet
Capacitor types
X7R vs C0G vs electrolytic — which dielectric for which job
Capacitor dielectric comparison
Rough guide for picking a capacitor family — always check the specific part's datasheet for voltage rating and tolerance.
| Type | Typical range | ESR | Polarized | Typical use |
|---|---|---|---|---|
| Ceramic (MLCC) — see the class table below | pF – µF | Low | No | Decoupling, filtering, general purpose |
| Film (PET/PP) | nF – µF | Very low | No | Audio, timing, precision analog |
| Aluminum electrolytic | µF – F | High | Yes | Bulk power supply filtering |
| Tantalum | µF range | Medium | Yes | Compact bulk filtering — fails short, use with care |
| Supercapacitor | F range | High | Yes | Energy buffering, memory backup |
Ceramic classes — X7R vs C0G
"Ceramic" is not one part. Class 1 (C0G/NP0) holds its value; Class 2 (X7R, X5R, Y5V, Z5U) trades that away for capacitance per unit volume. Two parts with the same printed value in the same package can differ by a factor of three once they are in the circuit.
| Code | Class | Temperature range & drift | Tolerance | Under DC bias | Use for |
|---|---|---|---|---|---|
| C0G / NP0 | 1 | −55…+125 °C, 0 ±30 ppm/°C | ±1 – ±5 % | None measurable | Timing, filters, oscillators, PLL loops — anything whose value has to stay put |
| X7R | 2 | −55…+125 °C, ±15 % | ±10 % | Large: often −50 % or worse near the rated voltage | Decoupling and bulk, where only "enough microfarads" matters |
| X5R | 2 | −55…+85 °C, ±15 % | ±10 – ±20 % | Large, same as X7R | Compact bulk in consumer gear — cheaper than X7R, but mind the 85 °C ceiling |
| Y5V | 2 | −30…+85 °C, +22 / −82 % | −20 / +80 % | Severe | Non-critical bypass only. At the top of its range most of the capacitance is gone |
| Z5U | 2 | +10…+85 °C, +22 / −56 % | −20 / +80 % | Severe | Legacy. Note it is not rated below +10 °C at all |
DC bias is the trap. A Class 2 part loses capacitance as you apply voltage across it, and the datasheet's headline value is measured at zero volts. A 10 µF 25 V X5R in an 0805 can measure 2–3 µF at 10 V — the part is not faulty, that is what it does. Two habits cover it: go one case size larger, and pick a voltage rating at least twice the working voltage for X7R/X5R bulk. C0G does not do this at all, which is why a timing capacitor is C0G and never X7R.
| Character | Meaning | ||
|---|---|---|---|
| 1st — low temp | X = −55 °C | Y = −30 °C | Z = +10 °C |
| 2nd — high temp | 4 = +65 °C | 5 = +85 °C | 6 = +105 °C · 7 = +125 °C |
| 3rd — drift | R = ±15 % | S = ±22 % | U = +22 / −56 % · V = +22 / −82 % |
