- Ceramic Capacitor Definition: A ceramic capacitor is a widely used electronic component that stores charge using a ceramic dielectric.
- Types of Ceramic Capacitors: There are two main types—Ceramic Disc Capacitors and Multilayer Ceramic Capacitors (MLCCs).
- Construction: MLCCs are made of multiple ceramic layers separated by metal electrodes, providing excellent high-frequency performance.
- Advantages: These capacitors are versatile, inexpensive, lightweight, and reliable, suitable for various applications.
- Applications: Ceramic capacitors are used in bypassing, decoupling, and frequency discrimination in electronic circuits.
What is a Ceramic Capacitor?
A ceramic capacitor is a common capacitor in an electronic circuit. Boards use it because the body is small and the dielectric is ceramic. The ceramic capacitor gets its name from its use of ceramic as a dielectric medium.
Ceramic capacitors are the usual high-frequency capacitors in boards. The parts are non-polar, so they have no polarity markings like an electrolytic capacitor.
This makes them easy to use in AC circuits. Values commonly run from about 1pF to 100μF. Voltage ratings run from a few volts on dense MLCCs to several kilovolts on some disc parts, not a single 10 V to 5000 V band for every type.
Types of Ceramic Capacitor
Construction-wise it can be subdivided into two groups
- Ceramic Disc Capacitor
- Multilayer Ceramic Capacitor (MLCC)
Ceramic Disc Capacitor
Ceramic disc capacitors have silvered electrodes on either side of a ceramic disc. Each electrode has a lead attached. The body is coated with a protective lacquer or epoxy, not a second ceramic dielectric.
The disc-type capacitors have a high capacitance per unit volume for a single-layer part. Many catalogue discs stop near 0.01 μF, though other values exist. One common class has voltage ratings around 750 V DC and 350 V AC. Those figures are product ratings, not a ceramic limit.
Multilayer Ceramic Capacitor
Multilayer ceramic capacitors (MLCCs) are made of several layers of ceramic, often barium titanate in Class 2 parts, separated by metal electrodes. Class 1 C0G parts use other ceramics. This design places many capacitors in parallel.
Some MLCCs have hundreds of ceramic layers, each acting as a separate capacitor. Class 2 layers are typically barium titanate and are separated by metal electrodes.
The terminal contacts are taken from both ends of the structure. Some MLCCs contain hundreds of ceramic layers, each layer only a few micrometers thick.
The total capacitance of the structure is about the capacitance of each layer times the number of layers in the capacitor, because the layers sit in parallel.
Multilayer construction plus surface mount can make a low-inductance high-frequency capacitor. Some small-value (e.g., tens of pico-farads) surface mount MLCCs can have self-resonant frequencies in the multiple gigahertz ranges.
Most older MLCCs were 1μF or less with voltage ratings of 50V or less. Low-voltage chips now reach tens to hundreds of microfarads. Close layer spacing still limits voltage on a given case size.
That same close spacing and high layer count let makers produce larger MLCCs, now commonly 10 to 100 μF at low voltage, not 10 to 100 pF. MLCCs suit high-frequency filtering and digital decoupling. Class 2 parts still lose capacitance with DC bias and temperature.
High-K (K= dielectric constant) ceramic capacitors are Class 2 parts. Capacitance drifts with time, temperature and frequency. Their main advantage is a higher capacitance-to-volume ratio than Class 1 C0G ceramics.
Class 2 parts are usually used in noncritical applications for bypassing, coupling and blocking. Voltage transients and flexure can crack the ceramic.
Do not use a high-K MLCC as the only bypass directly across a stiff low-impedance supply. Pair it with bulk capacitance, or the inrush and resonance can crack the chip or ring the rail.
Advantages of Ceramic Capacitor
The advantages of ceramic capacitors include:
- Any size or shape is available in the market.
- At the same time, ceramic capacitors are inexpensive.
- They are light in weight, too.
- Many MLCCs are rated around 100V. Disc ceramics go much higher.
- Their performance is reliable.
- They are suitable for use in hybrid integrated circuits.
Disadvantages of Ceramic Capacitor
The disadvantages of ceramic capacitors include:
- Very high-voltage MLCCs are uncommon. High-voltage disc ceramics exist.
- High capacitance at high voltage is still limited. Low-voltage MLCCs now reach 100μF and above.
Applications of Ceramic Capacitor
The medium and high permittivity ceramic capacitors are used for bypass and decoupling applications or frequency discrimination where Q factor and stability are not major issues.
