Ceramic capacitor
A ceramic capacitor stores energy in an electric field. After the charging transient, an ideal capacitor blocks steady DC while allowing changing signals to couple through it. Real parts have leakage, resistance and inductance, so their behaviour depends on frequency and operating conditions.
Two thin metal electrodes are separated by a slice of ceramic. When you apply voltage, charge piles up on each plate; the ceramic between them concentrates the electric field. The recipe of the ceramic (NP0/C0G, X7R, X5R, Y5V) controls how stable the capacitance stays across temperature and voltage.
In plain terms
A small charge reservoir made from metal electrodes and ceramic insulation. An MLCC stacks many of these layers to fit more capacitance into a small body.
Why designers use it
- Supplying transient current near an IC when the selected capacitance and layout meet its requirements.
- Shaping impedance in decoupling, filtering and bypass networks.
- Setting timing or filter behaviour with a suitable dielectric.
- Coupling changing signals while blocking a steady DC offset.
Best for
- Decoupling
- Filtering
- AC coupling
- Timing with a suitable dielectric
Key specifications
- Effective capacitance: Use the value under actual bias, temperature and ageing conditions
- Voltage: Check the exact series rating and application rules
- Dielectric: Compare temperature-compensating and high-dielectric-constant types
- Impedance: Check ESR, ESL and self-resonance at the operating frequency
- Mechanical reliability: Check assembly, board flex and termination requirements
When not to use it
- When the effective capacitance, voltage rating or physical size cannot meet the circuit's requirements.
- When the chosen dielectric's temperature, bias, ageing or acoustic behaviour is unsuitable.
- When the application requires safety approvals that the selected capacitor does not have.
Common mistakes
- Treating a high-dielectric-constant ceramic's nominal capacitance as its value at every operating voltage.
- Choosing a dielectric code without checking the actual part's bias and temperature curves.
- Ignoring mounting, connection inductance, cracking risk and circuit stability.
Where you will find it
- A power-rail decoupling design uses a selected MLCC to help supply transient current near an IC.
- A timing or filtering circuit can use a temperature-compensating ceramic when its stability and available capacitance suit the design.
- Murata's selection guide lists different ranges for surface-mount and leaded ceramics, illustrating why one numeric range is not a universal family limit.
A short history
Ceramic capacitors now include both disc and multilayer constructions. Stacking dielectric and electrode layers makes an MLCC compact, but dielectric choice still matters: temperature-compensating ceramics and high-capacitance ceramics have different stability and DC-bias behaviour. Miniaturisation does not make every ceramic capacitor interchangeable.
Good to know
- Adding electrode layers increases capacitance without changing the basic electric-field principle.
- Two capacitors with the same printed value can have different effective values on the same DC rail.
- A dielectric's temperature classification does not fully describe its DC-bias behaviour.