Ceramic capacitors are the most widely used capacitors in the electronic circuits. These capacitors are mainly used where small physical size and large charge storage is required. We know that capacitor is used to store the electric charge. ceramic disc capacitor , The technique used to store electric charge is same in all capacitors but the material used to construct the capacitor is different.
Construction of ceramic capacitor
In a ceramic capacitor, ceramic material is used to construct the dielectric and conductive metals are used to construct the electrodes. Dielectric is the insulating material placed between the electrodes of a capacitor.
Ceramic material is chosen as dielectric because of its great ability to allow electrostatic attraction and repulsion. Also, ceramic materials are poor conductors of electricity. Therefore, they do not allow flow of electric charges through them. On the other hand, electrodes of the ceramic capacitor are good conductors of electricity. Therefore, they easily allow electric current through them.
Different shapes of ceramic capacitor
Ceramic capacitors are available in the following shapes or forms:
- Ceramic disc capacitor
- Ceramic tubular capacitor
- Multilayer ceramic capacitor (MLCC)
Ceramic disc capacitor
The ceramic disc capacitors are made by coating silver on both sides of the ceramic disc. The ceramic disc acts as the dielectric and silver coated on both sides of the disc acts as electrodes. For low capacitance, a single ceramic disc coated with silver is used whereas for high capacitance multiple layers are used.
The leads made of copper are attached to the ceramic disc by using soldering technique. A protective coating is applied to the ceramic disc capacitor to protect it from heat.
The area of a ceramic disc or dielectric and spacing between the silver electrodes also determines the capacitance of the ceramic disc capacitor. The main disadvantage of using ceramic disc capacitor is its high capacitance change with slight change in temperature.
Ceramic tubular capacitor
As the name suggests, ceramic tubular capacitor is a hollow cylindrical ceramic material. The inner and outer surfaces of the hollow cylindrical ceramic material are coated with the silver ink. The hollow cylindrical ceramic material acts as the dielectric and the silver ink coated on inner and outer surfaces acts as electrodes.
Multilayer ceramic capacitor (MLCC)
The multilayer ceramic capacitor (MLCC) is made of multiple layers of ceramic material and conductive electrodes placed one above the other. The conductive electrodes are placed between each layer of ceramic material. In MLCC, the multiple layers of ceramic material acts as dielectric.
The multiple layers of ceramic and electrodes are contacted via the terminal surfaces. In this way, multiple layers of ceramic material and electrodes are constructed. Some MLCCs contain hundreds of ceramic layers and electrodes, each layer only a few micrometers thick.
The capacitance of each layer in MLCC is same. The total capacitance of MLCC is obtained by multiplying the capacitance of one layer by total number of layers.
For example, if each layer has capacitance of 2 pF and total layers in the MLCC are 50. The total capacitance is equal to 100 pF.
Total capacitance of MLCC = 2 pF × 50 = 100 pF
The capacitance of the MLCCs increases by reducing the space between the ceramic dielectric layers.
Applications of ceramic capacitors
The various applications of ceramic capacitors include:
- Tone compensation
- Automatic volume control filtering
- Antenna coupling
- Resonant circuit
- Volume control RF bypass
- Lighting ballasts
Advantages of ceramic capacitor
- High stability
- Low losses
- High capacitance
- Small size