Introduction of Capacitors

Capacitance is a physical quantity that characterizes the ability of a capacitor to hold charge. The amount of electricity we need to increase the potential difference between the two plates of the capacitor by 1 volt is called the capacitance of the capacitor. The symbol of the capacitor is C. Capacitors are one of the most widely used electronic components in electronic equipment. They are widely used in blocking, coupling, bypassing, filtering, tuning loops, energy conversion, control circuits, etc. At the same time, it is also one of the chip components largely used in SMT processing plants. Use C to represent capacitance, the capacitance units are farad (F), microfarad (uF), picofarad (pF), 1F=10*6uF=10*12pF

1 farad (F) = 1000000 microfarad (μF) 1 microfarad (μF) = 1000 nanofarad (nF) = 1000000 picofarad (pF)
Naming method of capacitors: The name type of domestic capacitors generally consists of four parts (not applicable to pressure-sensitive, variable, and vacuum capacitors). They respectively represent name, material, classification and serial number.

1. How to determine the polarity of electrolytic capacitors:

Just use a multimeter to measure. Discharge the electrolytic capacitor first, then connect the test leads of multimeter to both pins of capacitor. the big swing is positive pole, but pay attention to: The positive pole of the pointer multimeter is opposite to the negative pole of the capacitor, the opposite of the digital meter, and the capacitor must be discharged between two measurements. You can also use the length of the pin to distinguish the positive and negative poles. The long leg is positive and the short leg is negative; the black mark block on the capacitor is the negative pole. There are two semicircles silkscreen on the position of the capacitor on the PCB, and the pin corresponding to the colored semicircle is the negative electrode.

2. Classification of capacitors:

• According to its polarity, it is divided into two categories: polarized capacitors (such as electrolytic capacitors) and non-polarized capacitors.

• According to the structure, it is divided into three categories: fixed capacitors, variable capacitors and trimmer capacitors.

• Classified by electrolyte: organic dielectric capacitors, inorganic dielectric capacitors, electrolytic capacitors and air dielectric capacitors.

• According to the purpose, there are: high-frequency bypass, low-frequency bypass, filtering, tuning, high-frequency coupling, low-frequency coupling, and small capacitors.

3. Capacitor capacity mark:

• Direct marking method: Mark directly with numbers and unit symbols. For example, 01uF means 0.01 microfarad, some capacitors use "R" to indicate a decimal point, such as R56 means 0.56 microfarad.

•  Text symbol method: Use a regular combination of numbers and text symbols to indicate capacity. For example, p10 means 0.1pF, 1p0 means 1pF, 6P8 means 6.8pF, and 2u2 means 2.2uF.

• Color code method: use color circle or color dot to indicate the main parameters of the capacitor. The color code method of the capacitor is the same as the resistance.

Capacitor deviation symbol in China: +100%-0--H, +100%-10%--R, +50%-10%--T, +30%-10%--Q, +50%-20% --S, +80%-20%--Z.

4. Commonly used capacitors: 

Aluminum electrolytic capacitors, tantalum electrolytic capacitors, film capacitors, ceramic capacitors, monolithic capacitors, paper capacitors, trimmer capacitors, ceramic capacitors, glass glaze capacitors, mica and polystyrene dielectric capacitors.