What are the capacitor classifications?

Capacitance is one of the most widely used electronic components in electronic equipment. It is widely used in DC blocking, coupling, bypass, filtering, tuning loop, energy conversion, control circuit, etc. C is used to indicate capacitance, and the capacitance unit has Farah (F). Microfarad (uF), picofarad (pF), 1F=10^6uF=10^12pF

1. Model numbering method of capacitor

The model of domestic capacitors generally consists of four parts (not applicable to pressure sensitive, variable, vacuum capacitors). They represent the name, material, classification and serial number in turn.

Part Ⅰ: the name, expressed in letters, C.

Part Ⅱ: Materials, represented by letters.

PartⅢ: classification, generally expressed by numbers, individually represented by letters.

Part Ⅳ : serial number, represented by a number.

The material of the product is represented by letters: A-钽 electrolysis, non-polar film such as B-polystyrene, C-high frequency ceramic, D-aluminum electrolysis, E-other material electrolysis, G-alloy electrolysis, H-composite medium, I-glass glaze, J-metallized paper, L-polyester and other polar organic films, N-bismuth electrolysis, O-glass film, Q-paint film, T-low frequency ceramic, V-mica paper, Y-mica, Z - Paper

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2. Classification of capacitors

1). According to the structure, there are three categories: fixed capacitors, variable capacitors and trimmer capacitors.

2). According to electrolyte classification: organic dielectric capacitors, inorganic dielectric capacitors, electrolytic capacitors and air dielectric capacitors.

3). According to the purpose: high frequency bypass, low frequency bypass, filtering, tuning, high frequency coupling, low frequency coupling, small capacitor.

4). Frequency bypass: ceramic capacitors, mica capacitors, glass film capacitors, polyester capacitors, glass glaze capacitors.

5). Low frequency bypass: paper capacitor, ceramic capacitor, aluminum electrolytic capacitor, polyester capacitor.

6). Filtering: aluminum electrolytic capacitors, paper capacitors, composite paper capacitors, liquid tantalum capacitors.

7). Tuning: ceramic capacitors, mica capacitors, glass film capacitors, polystyrene capacitors.

8). High frequency coupling: ceramic capacitors, mica capacitors, polystyrene capacitors.

9). Low coupling: paper capacitors, ceramic capacitors, aluminum electrolytic capacitors, polyester capacitors, solid tantalum capacitors.

10). Small capacitors: metalized paper capacitors, ceramic capacitors, aluminum electrolytic capacitors, polystyrene capacitors, solid tantalum capacitors, glass glaze capacitors, metalized polyester capacitors, polypropylene capacitors, mica capacitors.

3. Common capacitors

1). Aluminum electrolytic capacitor

An electrolytic capacitor is immersed in a mixture of two aluminum foils, and a thin oxide film is used as a medium capacitor. Since the oxide film has a unidirectional conductive property, the electrolytic capacitor has a polarity and a large capacity. Tolerate large pulsating current, large capacity error, large leakage current; ordinary is not suitable for high frequency and low temperature applications, it is not suitable to use low frequency bypass, signal coupling, power supply filtering above 25kHz.

Capacity: 0.47--10000u

Rated voltage: 6.3--450V

Main features: small size, large capacity, large loss, large leakage

Applications: Power supply filtering, low frequency coupling, decoupling, bypassing, etc.

2). Tantalum electrolytic capacitor (CA) tantalum electrolytic capacitor (CN)

The sintered crucible is used as the positive electrode, and the temperature, frequency characteristics and reliability of the solid manganese dioxide used in the electrolyte are superior to those of the ordinary electrolytic capacitor, especially the leakage current is extremely small, the storage property is good, the service life is long, the capacity error is small, and the volume is small. The unit capacitance can get the largest capacitance voltage product tolerate the pulsating current, and if it is damaged, it is easy to be short-circuited in the ultra-small high-reliability mechanism.

Capacity: 0.1--1000u

Rated voltage: 6.3--125V

Main features: loss, leakage is less than aluminum electrolytic capacitor

Application: Replace aluminum electrolytic capacitors in circuits with high requirements

3). Film capacitor

The structure is similar to that of a paper capacitor, but a low-loss plastic material such as polyester or polystyrene is used as a medium with good frequency characteristics, a small dielectric loss cannot be made into a large capacity, a poor heat resistance filter, an integral, an oscillation, and a timing circuit. .

a. Polyester (Polyester) Capacitor (CL)

Capacity: 40p--4u

Rated voltage: 63--630V

Main features: small size, large capacity, heat and humidity resistance, poor stability

Application: Low frequency circuit with low stability and loss requirements

b. Polystyrene Capacitor (CB)

Capacity: 10p--1u

Rated voltage: 100V--30KV

Main features: stable, low loss, large size

Application: Circuits requiring high stability and loss

c. Polypropylene capacitor (CBB)

Capacity: 1000p--10u

Rated voltage: 63--2000V

Main features: performance similar to polystyrene but small size, slightly poor stability

Application: Replace most polystyrene or mica capacitors for higher requirements

4). Ceramic capacitor

A through-type or pillar-type ceramic capacitor, one of its electrodes is a mounting screw. The lead inductance is extremely small, the frequency characteristics are good, the dielectric loss is small, and the temperature compensation can not make a large capacity, and the vibration can cause a capacity change. Especially suitable for high frequency bypass.

a. High frequency ceramic capacitor (CC)

Capacity: 1--6800p

Rated voltage: 63--500V

Main features: low frequency loss, good stability

Application: high frequency circuit

b. Low frequency ceramic capacitor (CT)

Capacity: 10p--4.7u

Rated voltage: 50V--100V

Main features: small size, low price, large loss, poor stability

Application: low frequency circuit that is not required

5). Monolithic capacitor

 (Multilayer ceramic capacitor) is coated on several ceramic film blanks with electrode paddle material. After lamination, it is wound into an inseparable whole body at one time, and then encapsulated with resin to form small volume, large capacity, high reliability and resistance. High-temperature new capacitors, high-k dielectric low-frequency monolithic capacitors also have stable performance, small positive body, high Q-value error, noise bypass, filter, integral, and oscillating circuits.

Capacity range: 0.5PF--1UF

Withstand voltage: twice the rated voltage.

Large capacity, small size, high reliability, stable capacity, high temperature and humidity resistance, etc.

Applications: Widely used in electronic precision instruments. Various small electronic devices for resonance, coupling, filtering, bypass.

6). Paper capacitors

Generally, two aluminum foils are used as electrodes, and the capacitor paper having a thickness of 0.008 to 0.012 mm is alternately wound and separated. The manufacturing process is simple, the price is low, and a large capacitance can be obtained.

Generally, in low-frequency circuits, it is usually not used at frequencies higher than 3~4MHz. The oil-immersed capacitors have higher withstand voltage than ordinary paper capacitors and have good stability. They are suitable for high-voltage circuits.

7). Trimmer capacitor

The capacitance can be adjusted within a small range and can be fixed to a certain capacitance value after adjustment. The ceramic fine-tuning capacitor has a high Q value and a small volume, and can be generally divided into a round tube type and a wafer type. Mica and polystyrene media are usually spring-loaded east, simple in structure, but poor in stability. Wire-wound ceramic trimmer capacitors are copper wire <outer electrode> to change the capacitance, so the capacity can only be smaller. Not suitable for use in situations where repeated debugging is required.

a. Air medium variable capacitor

Variable capacitance: 100--1500p

Main features: low loss, high efficiency; can be made linear, linear wavelength, linear frequency and logarithmic, etc. according to requirements

Applications: electronic equipment, radio and television equipment, etc.

b. Thin film dielectric variable capacitor

Variable capacitance: 15-550p

Main features: small size, light weight; loss is greater than air medium

Applications: communications, broadcast receivers, etc.

c. Thin film dielectric trimmer capacitor

Variable capacitance: 1--29p

Main features: large loss, small size

Application: Circuit breaker, electronic instrument and other circuits for circuit compensation

d. Ceramic dielectric trimmer capacitor

Variable capacitance: 0.3--22p

Main features: low loss, small size

Application: Precision tuned high frequency oscillating circuit

8). Ceramic capacitor

Using a high dielectric constant capacitor ceramic (barium titanate titanate) extruded into a circular tube, a disk or a disk as a medium, and sintered by silver plating on a ceramic as an electrode. It is divided into high frequency. Both porcelain and low-frequency porcelain. Capacitors with small positive temperature coefficient of capacitance are used in high-stability oscillation circuits as loop capacitors and pad capacitors. Low-frequency ceramic capacitors are limited to circuits with lower operating frequencies. Road or DC-blocking, or where stability and loss are not critical (including high frequency). Such capacitors should not be used in pulse circuits because they are susceptible to breakdown by pulse voltage. High-frequency ceramic capacitors are suitable. In high frequency circuits.

9). Glass Glaze Capacitor (CI)

It is sprayed into a film by a special mixture suitable for spraying. The medium is sintered with a silver layer electrode to form a monolith. The structure performance is comparable to that of a mica capacitor. It can withstand various climatic environments. Generally, it can be used at 200. Working at °C or higher, the rated working voltage can reach 500V, and the loss is tgδ0.0005~0.008.

Capacity: 10p--0.1u

Rated voltage: 63--400V

Main features: good stability, low loss, high temperature resistance (200 degrees)

Applications: Pulse, Coupling, Bypass, etc.

4. Capacitor main characteristic parameters

1). Nominal capacitance and allowable deviation

The nominal capacitance is the capacitance that is marked on the capacitor. The deviation between the actual capacitance of the capacitor and the nominal capacitance is called the error, and the accuracy is called within the allowable deviation range.

Correspondence between accuracy level and allowable error: 00(01)-±1%, 0(02)-±2%, I-±5%, II-±10%, III-±20%, IV-(+20% -10%), V-(+50%-20%), VI-(+50%-30%). Generally, capacitors are commonly used in Class I, II, and III, and electrolytic capacitors are in Class IV, V, and VI, depending on the application.

2). Rated voltage

The maximum DC voltage RMS that can be continuously applied to the capacitor at the lowest ambient temperature and the rated ambient temperature is generally directly marked on the capacitor casing. If the operating voltage exceeds the capacitor's withstand voltage, the capacitor breaks down, causing irreparable permanent damage.

3). Insulation resistance

The DC voltage is applied to the capacitor and generates a leakage current. The ratio between the two is called the insulation resistance. When the capacitance is small, it mainly depends on the surface state of the capacitor. When the capacity is > 0.1 uf, it depends mainly on the performance of the medium. The larger the insulation resistance, the better.

The time constant of the capacitor: a time constant is introduced for proper evaluation of the insulation of the bulk capacitor, which is equal to the product of the insulation resistance of the capacitor and the capacity.

4). Loss

Under the action of electric field, the energy consumed by heat in unit time is called loss. All kinds of capacitors specify the allowable value of loss in a certain frequency range. The loss of capacitance is mainly caused by dielectric loss, conductance loss and all metal parts of capacitance. Caused by the resistance.

Under the action of DC electric field, the loss of capacitor exists in the form of leakage conduction loss, which is generally small. Under the action of alternating electric field, the loss of capacitance is not only related to leakage conduction, but also related to the periodic polarization establishment process.

5). Frequency characteristics

As the frequency increases, the capacitance of the capacitor generally shows a decreasing law.

5. Capacitor capacity indication

1). Straight standard method

Directly marked with numbers and unit symbols. For example, 01uF means 0.01 microfarads, and some capacitors use "R" to indicate a decimal point. For example, R56 represents 0.56 microfarads.

2). Text notation

A regular combination of numbers and literal symbols is used to indicate capacity. For example, p10 represents 0.1pF, 1p0 represents 1pF, 6P8 represents 6.8pF, and 2u2 represents 2.2uF.

3). Color scale method

The main parameters of the capacitor are represented by color circles or color points. The color code method of the capacitor is the same as the resistance.

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