What Is a Ceramic Capacitor?
A ceramic capacitor is a capacitor that uses ceramic as the derivative.
The capacitor consists of two metal plates and a derivative sandwiched between the metal plates. Several materials are used As a derivative of the capacitor, each with its own characteristics.
Ceramic capacitors are characterized by their high dielectric constant, small size, and heat resistance. Furthermore, as capacitors with good frequency characteristics, they are often used in high-frequency circuits.
Uses of Ceramic Capacitors
Ceramic capacitors are used as bypass capacitors in digital circuits. A capacitor is characterized by its ability to pass AC current but not DC current.
Ceramic capacitors are used as coupling capacitors or line filters because of their ceramic properties. Examples include AC/DC and DC/DC converter circuits and circuits for circuit breakers.
They are also widely used to cancel high and low frequency noise.
Principle of Ceramic Capacitors
The principle of a ceramic capacitor is the same as that of a general capacitor. In principle, a ceramic dielectric is placed between two electrodes, and when a voltage is generated between the electrodes, electric charge is stored in the electrodes. Thereafter, the stored electric charge is released as charge by the capacitor.
The capacity of the charge stored by a capacitor is called capacitance. The capacitance and its properties vary depending on the material of the dielectric, the distance between the electrodes, and the number of dielectric layers.
Ceramic derivatives with high inductivity are used. The main materials used are titanium dioxide and alumina. Barium titanate is also used, but it is slightly more expensive. Although expensive, Barium titanate capacitors have higher capacitance.
Types of Ceramic Capacitors
Ceramic capacitors are classified into three main types, namely: low dielectric constant type, high dielectric constant type, and semiconductor type.
1. Low Dielectric Constant Type
Titanium dioxide is used as the main dielectric. It is resistant to temperature change, used for coupling and for temperature compensation.
2. High Dielectric Constant Type
Barium titanate is used as the dielectric, and its dielectric constant is higher than that of titanium dioxide. It has a high capacitance and is used for smoothing circuits. However, it is somewhat expensive.
3. Semiconductor Type
Semiconductor type uses semiconductor ceramics such as strontium titanate as the dielectric. It is considered a compact capacitor with large capacitance and good insulation properties. It is the most expensive of the three.
Other Information on Ceramic Capacitors
1. How to Read Ceramic Capacitor Capacitance
Ceramic capacitors do not directly state their capacitance such as “0.1 uF” or “10 uF” due to their small body size, but only use 1 to 3 digits to indicate the capacitance.
In the Case of 1 to 2 Digits
In the case of 1- to 2-digit numbers, the capacitance is simply the number read as it is and the unit of “pF (picoFarad)” is added. For example, “5” is 5pF and “33” is 33pF.
The smaller the number, the smaller will be the capacitance, while the smaller the capacitor, the smaller the size of the body.
In the case of 3 digits
In the case of 3-digit capacitors, as with carbon film resistors, the upper two digits are read as numerical values, while the third digit is multiplied as a multiplier. The unit is also “pF”. For example, “104” is 10 x 10 to the 4th power = 100000pF = 100nF = 0.1uF, and “223” is 22 x 10 to the 3rd power = 22000pF = 22nF = 0.022uF.
On the other hand, many chip-type ceramic capacitors do not indicate the capacitance on the body. It is recommended to check the capacitance with a tester capable of measuring capacitance before mounting or replacing parts, such as removing the capacitor from the tape just before use or storing it in a case that can be divided into smaller pieces.
2. Polarity of Ceramic Capacitors
In general, ceramic capacitors have no polarity and can be mounted in either direction in a circuit. In the case of leaded components, since the capacitance is printed on only one side, the sides with the capacitance printed on them should basically face the same direction.
If there are taller components nearby, mount them in an orientation that allows the values to be read later, so that the board is easy to see when checking.
3. Withstand Voltage of Ceramic Capacitor
Ceramic capacitors have an upper limit for the voltage that can be applied. However, depending on the size and rating of the capacitor itself, it may not be specified on the body or may be specified as an abbreviation.
When using capacitors in circuits that handle particularly high voltages, please check the data sheet or manufacturer’s model number carefully. This is because the manufacturer’s model number, which is a long list of alphanumeric characters, may contain information on withstand voltage.