Capacitor is composed of two conductors which are insulated from each other, and the dielectric is inserted between the conductors. The capacitor is represented by the letter C, whose definition is c=q/u, where C is the capacitance, unit farad (the symbol f), q is the charge quantity and unit Coulomb (the symbol C), and u represents the voltage and unit volt (V for short). The electric field between two plates is used to store the charge. The number of charges on the two plates is equal, and the symbol is opposite. According to the difference of dielectric between plates, it can be divided into paper dielectric capacitor, porcelain dielectric capacitor, film capacitor, glass glaze capacitor, mica capacitor, etc.

Introduction to capacitor knowledge - aluminum electrolytic capacitor

Aluminum electrolytic capacitor is a kind of capacitor with thin oxide film as dielectric, and is wrapped between two aluminum foil and wrapped with absorbent paper soaked with paste electrolyte. Because the oxide film has single conductivity, the electrolytic capacitor has polarity. The characteristics are as follows:

1. the aluminum electrolytic capacitor has a large capacity and can bear large pulsating current.

2. the capacity error of aluminum electrolytic capacitor is large and leakage current is large; the common one is not suitable for high frequency and low temperature application, and it should not be used at frequency above 25kHz.

3. aluminum electrolytic capacitor has the characteristics of low frequency bypass, signal coupling and power filter.

Introduction of capacitor knowledge tantalum electrolytic capacitor

The positive electrode is sintered by tantalum block, and solid manganese dioxide is used as the main material of electrolyte. Temperature characteristics, frequency characteristics and reliability are much better than ordinary electrolytic capacitors, especially the leakage current is very small and good storage performance, longer service life, smaller capacity error, small volume, maximum capacitor product (per unit volume). However, the ability of tantalum electrolytic capacitor to withstand pulsating current is very poor. If damaged, tantalum electrolytic capacitor is easy to short circuit. Tantalum electrolytic capacitors are usually used for ultra small and highly reliable parts.

Introduction to capacitor knowledge metallized paper dielectric capacitor

Two metal foils are used as electrodes, sandwiched in extremely thin capacitor paper, and then rolled into cylindrical or flat cylindrical core, and then sealed in metal shell or insulating material (such as fire paint, ceramics, glass glaze, etc.). It is characterized by small volume and large capacity. But the inherent inductance and loss are relatively large, which are suitable for low frequency circuits.

Introduction to capacitor knowledge - self healing parallel capacitor

It is similar to paper capacitors in structure, but uses low loss plastic materials (such as polyester and polystyrene) as the medium. The features are as follows:

1. the self healing parallel capacitor has good frequency characteristics and low dielectric loss.

2. the self healing parallel capacitor can not be made into large capacity and has poor heat resistance.

3. filter, integral, oscillation and timing circuit. One electrode of porcelain capacitor is mounting screw. The lead inductance is very small, the frequency characteristic is good, the dielectric loss is small, and the temperature compensation function is available.

4. the self healing parallel capacitor cannot be made into large capacity, because vibration will cause capacity change.

5. self healing parallel capacitor is particularly suitable for high frequency bypass.

Knowledge explanation of capacitor mica capacitor

The electrode plate is made of metal foil or silver coating on mica sheet,

After laminating the plate and mica layer by layer, the die casting is made in the rubber powder or sealed in the epoxy resin. The characteristics of the method are small dielectric loss and high insulation resistance. The temperature coefficient is small, and it is suitable for high frequency circuit.

Introduction to capacitor knowledge - single stone capacitor

Several ceramic thin film blanks are covered with electrode slurry materials. After lamination, they are wrapped into an integral part at a time, and then sealed with resin outside. The single stone capacitor is a new type of capacitor, which has the characteristics of small volume, large capacity, high reliability and high temperature resistance. Besides, the single stone capacitor has the characteristics of stable performance, small volume and large capacity error. In general, two aluminum foils are used as electrodes and capacitor paper of thickness 0.008 to 0.012mm is separated and wound by overlapping. The manufacture process of single stone capacitor is simple, the price is low, and the larger capacitance can be obtained.

Capacitor knowledge explanation - film capacitor

The structure is the same as that of paper dielectric capacitor, and the medium is polyester or polystyrene. Polyester film capacitance, high capacitance, small volume, large capacity, good stability, suitable for bypass capacitance. Polystyrene film capacitor, with small dielectric loss, can not be made into large capacity and high insulation resistance, but the temperature coefficient is large, which can be used in high frequency circuits.

Introduction to capacitor knowledge metallized polypropylene capacitor

Usually in low frequency circuits, it is not usually used at frequencies higher than 3-4mhz. The oil immersed capacitor has higher voltage resistance and better stability than the ordinary paper capacitor. They are suitable for high voltage circuit fine tuning capacitors (semi variable capacitors). Metallized polypropylene capacitors can adjust capacitors in a small range and can be fixed to specific areas after adjustment.

The fine tuning capacitors with ceramic dielectric have the characteristics of high charge and small size, which are usually divided into two types: round tube type and circular plate type. Spring type elements are usually used in mica and polystyrene media, which have simple structure but poor stability. The wire wound ceramic fine-tuning capacitor can change the capacitance by removing copper wire (external electrode), so it can only reduce the capacitance. Therefore, metallized polypropylene capacitor is not suitable for the occasion that need to be adjusted repeatedly.

Introduction to capacitor knowledge ceramic capacitor

The high dielectric constant capacitor ceramic (titanium titanate oxide) is extruded into a round tube, a circular plate or a disc as the medium, and silver is plated on the ceramic as an electrode by the burning infiltration method. It also includes high frequency porcelain and low frequency porcelain medium. The capacitor with small positive capacitance temperature coefficient is used as loop capacitor and pad capacitor in high stable oscillation circuit.

Low frequency porcelain capacitors are limited to bypass or DC isolation in the circuit with low operating frequency, or in the case of low stability and loss requirements (including high frequency). This kind of capacitor is not suitable for use in pulse circuit, because they are easy to be broken down by pulse voltage.

Introduction to capacitor knowledge glass glaze capacitor

The structure properties of "single stone" formed by sintering of silver layer electrode in medium can be compared with mica capacitor. The utility model has the advantages of porcelain dielectric capacitor, and has smaller volume and high temperature resistance.

The electrodes of the capacitors are insulated from each other, so the capacitors can be separated from the direct flow and exchange. The capacitor can store the charge property, and can play the role of rectifying and filtering in the circuit. When the capacitor is charged and discharged, the voltage cannot be changed, so it can be used to shift phase and be used as starting capacitor in the motor. In short, capacitors can play different roles in different circuits, and they have a wide range of applications. They are no exception in the miniaturization era of electronic products.