Capacitors
The second-most-common part. Most are doing one of three jobs: decoupling, bulk energy storage, or filtering / DC blocking.
Common use cases​
| Value | Typical job |
|---|---|
| 100 nF (0.1 µF) | Decoupling — one per IC power pin, right at the pin |
| 1 µF – 10 µF | Bulk decoupling per supply rail near the chip |
| 10 µF – 100 µF+ | Bulk at the regulator input/output |
| pF range | Crystal load caps, RC/EMI filters, feedback |
| series cap | DC blocking / AC coupling (e.g. audio, high-speed) |
Dielectric types (this matters)​
| Type | Class | Use for | Watch out |
|---|---|---|---|
| C0G/NP0 | Ceramic I | Timing, filters, small precise values | Small capacitance only |
| X7R/X5R | Ceramic II | Decoupling, bulk MLCC | DC-bias derating (see below) |
| Electrolytic | — | Big bulk, low cost | Polarised, ages, ESR |
| Tantalum/polymer | — | Compact bulk, stable | Polarised; tantalum fails short |
| Film | — | Audio, snubbers, high-V | Bulky |
MLCC DC-bias derating
An X5R/X7R ceramic loses a big fraction of its capacitance under DC voltage — a "10 µF" cap may deliver 3–4 µF at its rated voltage. Over-spec the voltage rating (e.g. use a 25 V part on a 5 V rail) and don't trust the headline value for bulk.
Decoupling — the rule​
- 100 nF per power pin, placed at the pin with a short via to ground.
- Add bulk (1–10 µF) per rail near the chip; big bulk at the regulator.
- Short, wide connections; the loop from cap to pin to ground must be tiny (it's an SI/EMI issue).
See also​
- MCU & Digital Circuits — decoupling in context
- Power Supplies
- Copper Pours & Thermal — plane capacitance