Ceramic Capacitor: What is it?

What is a Ceramic Capacitor?

A ceramic capacitor is the most commonly used capacitor in an electronic circuit. A ceramic capacitor is used due to its small physical size and large charge storage capability. The ceramic capacitor gets its name from its use of ceramic as a dielectric medium.

Ceramic capacitors are known as the “workhorses” of high-frequency capacitors. They are non-polar, meaning they do not have polarity markings like electrolytic capacitor.

This makes them easy to use in AC circuits. Ceramic capacitors are typically made with values from 1pF to 100μF and can handle DC voltages from 10 volts to 5000 volts.

Types of Ceramic Capacitor

Construction-wise it can be subdivided into two groups

1. Ceramic Disc Capacitor
2. Multilayer Ceramic Capacitor (MLCC)

Ceramic Disc Capacitor

Ceramic disc capacitors have two conductive discs on either side of a ceramic insulator. Each disc has a lead attached and is coated with a waterproof ceramic material.

The disc-type capacitors have a high capacitance per unit volume. They are available up to a value of 0.01 μF. It has voltage ratings up to 750 V D.C. and 350V concerning A.C.

Multilayer Ceramic Capacitor

Multilayer ceramic capacitors (MLCCs) are made of several layers of ceramic material, usually barium titanate, separated by metal electrodes. This design places many capacitors in parallel.

Some MLCCs have hundreds of ceramic layers, each acting as a separate capacitor. These layers are typically made of 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 would be the product of the capacitance of each layer and the total number of layers in the capacitor.

Multilayer capacitor construction, when combined with surface mount technology, can produce almost ideal high-frequency capacitors. Some small-value (e.g., tens of pico-farads) surface mount MLCCs can have self-resonant frequencies in the multiple gigahertz ranges.

Most MLCCs have capacitance values of 1μF or less with voltage ratings of 50V or less. The small spacing between the layers limits the voltage rating.

However, the small spacing combined with a large number of layers has allowed manufacturers to produce more substantial value MLCC with capacitance values in the 10 to 100 pf range. MLCCs are excellent high-frequency capacitors and commonly used for high-frequency filtering as well as digital logic decoupling applications.

High-K (K= dielectric constant) ceramic capacitors are only medium-frequency capacitors. They are relatively unstable to time, temperature, and frequency. Their primary advantage is a higher capacitance-to-volume ratio, compared with that of standard ceramic capacitors.

They are usually used in noncritical applications for bypassing, coupling, and blocking. Another disadvantage is that voltage transients can damage them.

It is therefore not recommended to use as bypass capacitors directly across a low-impedance power supply.

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.
• They can be designed to withstand up to sufficient high voltage (up to 100V).
• 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 ceramic capacitors are not available.
• High capacitance values are not possible.

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.