Types of Capacitors introduction and Their Uses

Capacitors are the most common passive components used in circuit design. Its function is to block the AC current while pass the DC current, and it also has the function of power storage, and has a good filtering effect, which can output the pulsating signal in a smooth way. The application of capacitors in electronics is very common. Let's talk about the common types of capacitor in circuits and their uses.

Virtually all types of capacitor are available as following:

Material: Use ceramic material as medium, coat a layer of metal (silver) film on its surface, and then sinter at high temperature as an electrode. Ceramic capacitors are divided into Class 1 dielectrics (NPO, CCG); Class 2 dielectrics (X7R, 2X1) and Class 3 dielectrics (Y5V, 2F4).

Types: Ceramic capacitors are divided into two types: high-frequency ceramics and low-frequency ceramics. Capacitors with a small positive temperature coefficient of capacitance are used in highly stable oscillation circuits as loop capacitors and pad capacitors. Low-frequency ceramic capacitors are limited to bypassing or blocking DC in circuits with lower operating frequencies, or occasions (including high frequencies) that do not require high stability and loss. Such capacitors should not be used in pulsed circuits because they are prone to breakdown by pulsed voltages.

Features: Class 1 have the advantages of small temperature coefficient, high stability, low loss and high withstand voltage. The maximum capacity does not exceed 1000pF, commonly used are CC1, CC2, CC18A, CC11, CCG and other series. Mainly used in high frequency circuits.

Class 2 and Class 3 are characterized by high dielectric coefficient, large capacity (up to 0.47μF), small volume, and poor loss and insulation compared to Class 1. 

Application Models: Widely used in medium and low frequency circuits for DC blocking, coupling, bypassing and filtering capacitors, and commonly used are CT1, CT2, CT3 and other three series.

Material: A non-polar capacitor with a positive temperature coefficient (that is, when the temperature increases, the capacitance becomes larger) made of polar polyester film as the medium.

Advantages: High temperature resistance, high pressure resistance, moisture resistance and cheap price, suitable for bypass capacitors.

Application Models: Generally used in medium and low frequency circuits, and commonly used models are CL11, CL21 and other series.

Value Identification: Internationally, the withstand voltage value of capacitors is usually represented by letters. The common correspondence between codes and bases is:

A: 1.0; B: 1.25; C: 1.6; D: 2.0; E: 2.5; F: 3.15; G4.0;

H: 5.0; J: 6.3; K: 8.0; Z: 9.0;

The number in front of the letter represents the power of 10, for example, 2A is 102*1.0=100V, 2C is 102*1.6=160V and so on.

The letters behind the withstand voltage value represent the capacitance in pF.

For example, 823 means the capacity is 82*10^3=82000Pf, 224 means 22*104=220000pf=0.22μF. The last letter means the precision, such as J means the capacity tolerance is ±5% and so on.

Typical capacitor identification example: 2A823J is 82000Pf±5%, withstanding voltage 100V.

Material: There are two types of foil type and metallized type.

Advantages: Foil type has large insulation resistance, low dielectric loss, stable capacity and high precision, but large volume and poor heat resistance; metallized type has good moisture resistance and stability, and can recover after breakdown, also it has advantages of the low insulation resistance and poor high frequency characteristics.

Application Models: Generally used in medium and high frequency circuits, and commonly used models are CB10, CB11 (non-sealed foil type), CB14~16 (precision type), CB24, CB25 (non-sealed metallization), CB80 (high pressure type), CB40 (sealed metallization) and other series. In short, they used in various precision measuring instruments, car radios, industrial proximity switches and high-precision digital-to-analog converter circuits.

Material: It is a negative temperature coefficient non-polar capacitor that made of non-polar polypropylene film as the medium. There are two types of unsealed (commonly encapsulated with colored resin paint) and sealed (encapsulated with metal or plastic housing).

Advantages: Small loss, stable performance, good insulation and large capacity.

Application Models: Generally used in medium and high frequency circuits or as starting capacitors for motors, and commonly used foil polypropylene capacitors include CBB10, CBB11, CBB60, CBB61, etc.; metallized polypropylene capacitors include CBB20, CBB21, and CBB401 series.

CBB capacitor series are used in high frequency and high power circuits such as filtering, cross-line, resonance, etc.

Material: Multi-layer laminated ultra-miniature capacitors sintered with barium titanate-based ceramic materials.

Advantages: It has the advantages of reliable performance, high temperature resistance, moisture resistance, large capacity (range 1pF~1μF), and small leakage current.

Disadvantages: Low working voltage (withstand voltage lower than 100V).

Application Models: Widely used in resonance, bypass, coupling, filtering, etc, and commonly used are CT4 (low frequency), CT42 (low frequency), CC4 (high frequency), CC42 (high frequency) and other series.

Classification

It is a temperature-compensated NPO dielectric. The electrical performance of this capacitor is the most stable and basically does not change with temperature, voltage and time. In short, it is an ultra-stable, low-loss capacitor material type and is suitable for high stability and reliability requirements. frequency, UHF and VHF circuits.

It is a high dielectric constant X7R series, so it can make capacitors with larger capacity than NPO dielectrics. This kind of capacitor has relatively stable performance. With the change of temperature, voltage and time, its unique performance does not change significantly. It is a type of stable capacitor material. It is used in DC blocking, coupling, bypass, filter circuit and frequency circuit with high reliability requirements.

It uses Y5V dielectric. This capacitor has a high dielectric constant and is often used in the production of large-capacity capacitors with larger specific capacitance and higher nominal capacity. However, its capacity stability is worse than that of X7R, and its capacity and loss are more sensitive to test conditions such as temperature and voltage. It is mainly used in oscillation, coupling, filtering and bypass circuits in electronic complete machines.

Monolithic ceramic capacitors are larger than ordinary ceramic capacitors (10pF~10μF), and have the advantages of large capacitance, small size, high reliability, stable capacitance, high temperature resistance, good insulation, and low cost, so they are widely used. They can not only replace mica capacitors and paper capacitors, but also replace some tantalum capacitors, and are widely used in small and ultra-small electronic devices (such as liquid crystal watches and micro instruments).

Material: Mica is used as the medium, and a layer of metal film (silver) is sprayed on the surface as the electrode, which is laminated according to the required capacity and then dipped and compressed in the bakelite shell (or ceramic or plastic shell).

Advantages: Good stability, small distributed inductance, high precision, low loss, large insulation resistance, good temperature characteristics, that is, good frequency characteristics, high operating voltage (50V~7kV) and so on.

Application: It is generally used for signal coupling, bypassing, tuning, etc. in high-frequency circuits. For example, they are common in occasions that require high stability and reliability of capacitors, such as instruments and meters of electronic, power and communication equipment, and are also used in aerospace, aviation, navigation, rockets, satellites, military electronics, and oil exploration equipment. Commonly used ones are CY, CYZ, CYRX and other series.

Material: The thin capacitor special paper is used as the medium, and the aluminum foil or lead foil is used as the electrode.

Advantages: The capacitance (100pF~100μF) has a wide working voltage range, and the maximum withstand voltage value can reach 6.3kV.

Disadvantages: Large size, low capacity accuracy, large loss, and poor stability.

Classification: Paper capacitors are divided into inductive type and non-inductive type according to winding methods. The inductive core is actually a ribbon coil with many turns, so the inductance is large. The non-inductive type is to stagger the electrode foils to both sides of the paper, so that the sides of the foil strips extend out of the paper strips, and then the leads are welded after winding into a cylindrical core. In this way, the coils of the electrode foil are short-circuited with each other, so the inductance is very small. This capacitor can be used at higher frequencies.

Application Models: Common ones are CZ11, CZ30, CZ31, CZ32, CZ40, CZ80 and other series.

Structure: Using vacuum evaporation technology, a layer of metal film is evaporated on the paper coated with paint film as an electrode.

Advantages: Compared with ordinary paper capacitors, it is small in size, large in capacity, and has strong recovery ability after breakdown, which is an unique characteristic. For common situation, when the paper-dielectric capacitor is broken down, the paper medium is scorched, and the two layers of metal foil are melted together at the breakdown place to form a short circuit. But for metallized paper capacitors, the metal film at the breakdown place evaporates at high temperature, leaving only insulating holes and no short circuit.

Application Models: Common ones are CJ10, CJ11 and other series.

Material: The polar one is made by winding the aluminum foil (positive electrode) with an oxide film and the backing paper impregnated with the electrolyte solution together with the cathode foil lamination. Appearance package has tube type and vertical type. And there is a blue or black plastic cover outside the aluminum shell.

Advantages: The capacity range is large, generally 1~10000μF, and the rated working voltage range is 6.3V~450V.

Disadvantages: Medium loss, large capacity error (maximum allowable deviation is +100%, -20%), poor high temperature resistance, long storage time and unstable working state.

Application: Usually used in DC power circuits or medium and low frequency circuits for filtering, decoupling, signal coupling, time constant setting, and DC blocking. Note that the polarity cannot be reversed when used as a filter capacitor in a DC power supply.

Selection: The capacity and withstand voltage marked on the body of the aluminum electrolytic capacitor are very important and are the most basic content for selecting capacitors. In the actual selection of capacitors, a capacitor with a larger capacity should be used for places where the current changes rapidly, but it’s not always good. First, the larger the capacity, the higher the cost and volume. In addition, the larger the capacitor, the higher the charging current. The bigger it is, the longer the charging time will be. These are all to be considered in practical application selection.

Material: There are two forms:

1) The foil type tantalum electrolytic capacitor adopts a winding core inside, the negative electrode is liquid electrolyte, and the medium is oxidized tantalum. Common models are CA30, CA31, CA35, CAk35 series.

2) The tantalum powder sintered positive electrode is sintered with very fine tantalum powder blocks. Packaging comes in many forms. Widely used models include CA41, CA42, CA42H, CA49, CA70 (non-polar) and other series.

Advantages:

1) Small Size

Since capacitors use tantalum powder with very fine particles, and the dielectric constant ε of the tantalum oxide film is 17 higher than that of the aluminum oxide film, the capacitance per unit volume of the tantalum capacitor is large.

2) Wide Operating Temperature Range

Generally, tantalum electrolytic capacitors can work normally under the temperature of -50℃~100℃. Although aluminum electrolytic capacitors can also work in this range, their electrical performance is far inferior to that of them.

3) Long Life, High Insulation Resistance and Small Leakage Current

The tantalum oxide film dielectric in tantalum electrolytic capacitors is not only resistant to corrosion, but also maintains good performance for a long time.

4) Good Impedance Frequency Characteristics

For capacitors with poor frequency characteristics, when the operating frequency is high, the capacitance drops significantly, and the loss (tgδ) also rises sharply. But solid electrolytic capacitors can work above 50kHz. As the frequency increases, the capacity of capacitors also decreases, but the decrease is small. Some data show that the capacity decreases by less than 20% when working at 10kHz, while the capacity of aluminum electrolytic capacitors decreases by 40%.

5) High Reliability

The chemical properties of the tantalum oxide film are stable, and because the tantalum anode substrate Ta2O5 is resistant to strong acids and alkalis, it can use solid or acid-containing liquid electrolytes with low resistivity, which makes the loss of tantalum electrolysis smaller than that of aluminum electrolytic capacitors, and the temperature stability is good.

Disadvantages: High production cost and low pressure resistance.

Application: Widely used in various medium and low frequency circuits and time constant setting circuits in communications, aerospace, military and household appliances.

With the properties of storing electricity, charging and discharging, etc, they are mainly used in filtering, energy storage and conversion, mark bypass, coupling and decoupling, and time constant components. Pay attention to its performance characteristics in application, and correct use will help to give full play to its functions, such as considering the working environment of the product and its heating temperature, and taking measures such as derating, if it is used improperly, it will affect the service life of the product.

A variable capacitor is a capacitor whose capacitance can be adjusted within a certain range. When the relative effective area between the pole pieces or the distance between the pieces changes, its capacitance changes accordingly. Usually used as a tuning capacitor in a radio receiving circuit. Here are several types as following:

Material: It consists of a fixed piece and a moving piece. The fixed piece is a metal piece, and a layer of mica flakes is the most medium on its surface. The moving piece is an elastic copper or aluminum piece. Adjust the moving piece and the fixed piece by adjusting the screws on the moving piece, then the distance between the slices changes the capacitance. There are single trimmers and double trimmers.

Advantages: The capacitance can be adjusted repeatedly.

Application: Used in transistor radios, electronic instruments, and electronic equipment.

Material: Ceramic is used as the medium, and the semicircular silver layer is plated on both the moving plate and the stator. By rotating the moving plate to change the relative position between the two silver plates, the size of the capacitance can be changed.

Advantages: Small size, can be adjusted repeatedly, easy to use.

Application: Used in transistor radios, electronic instruments, and electronic equipment.

Material: Use organic plastic film as a medium, that is, add it between the moving piece and the fixed piece. Adjust the screw on the moving piece, and make the moving piece rotate to change the capacity. Film trimmer capacitors are generally divided into double trimmers and quadruple trimmers. Some sealed double-connected or four-connected variable capacitors have their own thin-film trimmer capacitors, which are installed on the top of the casing, making it easier to use and adjust.

Advantages: With small size, light weight, it can be adjusted repeatedly and is easy to use.

Application: Used in transistor radios, electronic instruments, and electronic equipment.

Material: The electrode consists of two sets of metal sheets. One set is the fixed piece, the other is the moving piece, and the air is used as the medium between them. When the rotor is rotated to make it all screw into the stator, its capacitance is the largest, on the contrary, when the rotor is fully screwed out of the stator, the capacitance is the smallest. Air variable capacitors are divided into single-connection and double-connection.

Advantages: It is easy to adjust, with stable performance, and not easy to wear.

Disadvantage: Bulky.

Application: Used in radios, electronic instruments, high-frequency signal generators, and communication electronic equipment.

Material: A plastic film is added between the moving piece and the stator as a medium, and the shell is encapsulated by transparent or translucent plastic, so it is also called a sealed double-connected and four-connected variable capacitor.

Advantages: Small size and light weight.

Disadvantages: It is easy to wear.

Uses: Single connection is mainly used in simple radios or electronic instruments; double connection is used in transistor radios and electronic instruments and electronic equipment; quadruple connection is commonly used in AF/FM multi-band radios.

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