Basic knowledge of Capacitance

Commonly used capacitors According to the media are divided into paper dielectric capacitance, oil-impregnated paper dielectric capacitance, metallized paper dielectric capacitance, mica capacitors, film capacitors, ceramic capacitors, electrolytic capacitors and so on.

Table 1 The structure and characteristics of commonly used capacitors

Capacitance type	Capacitance structure and characteristics
Paper dielectric capacitance	Electrodes are made of two pieces of metal foil, sandwiched in extremely thin capacitance paper, rolled into cylindrical or flat cylindrical cores, and then sealed in metal shells or insulating materials such as wax, ceramics, glass glaze, etc. It is characterized by a small volume and can be done with greater capacity. However, the intrinsic inductance and loss are relatively large, suitable for low frequencies.
Mica Capacitor	With metal foil or on the Mica film sprayed silver layer made electrode plate, plate and mica layer after laminated, and then die-casting in bakelite powder or sealed in epoxy resin made. It is characterized by small dielectric loss, large insulation resistance, low temperature coefficient, suitable for high-frequency circuits.
ceramic Capacitor	The ceramic substrate is sprayed on both sides of the silver layer, and then sintered Silver Film plate made. It is characterized by small size, good heat resistance, low loss, high insulation resistance, but small capacity, suitable for high-frequency circuits. Ferroelectric ceramic capacitance is larger, but the loss and temperature coefficient is large, suitable for low-frequency circuit.
Film Capacitors	The structure and the paper dielectric capacitance are the same, the medium is polyester or polystyrene. Polyester film capacitance, high dielectric constant, small size, large capacity, good stability, suitable for bypass capacitor. Polystyrene film capacitors, dielectric loss is small, high insulation resistance, but the temperature coefficient is large, can be used in high-frequency circuit.
Metallized paper Dielectric capacitance	The structure and the paper dielectric capacitance are basically the same. It is on the capacitor paper coated with a layer of metal film to replace the metal foil, small size, large capacity, generally used in low-frequency circuits.
Oil impregnated paper dielectric capacitance	It is the paper dielectric capacitance immersed in the specially treated oil, can enhance its pressure resistance. It is characterized by large capacitance, high pressure, but larger volume.
Aluminum Electrolytic Capacitors	It is made of aluminum cylinder cathode, which contains a liquid electrolyte, inserted into a curved aluminum band made of the anode. Also need to pass the DC voltage processing, so that the anode film formed a layer of oxide film to do the media. It is characterized by large capacity, but the leakage of large, poor stability, positive and negative polarity, suitable for power filter or low-frequency circuit. When used, do not reverse the positive or negative polarity.
Tantalum and niobium electrolytic capacitors	It uses metal tantalum or niobium as the cathode, with dilute sulfuric acid and other liquid to do the cathode, with tantalum or niobium oxide film produced by the surface made of media. It is characterized by small size, large capacity, stable performance, long life, high insulation resistance, good temperature characteristics. Used in high-demand equipment.
Half variable capacitance	Also known as trimmer capacitors. It is made of two or two sets of small metal shrapnel, sandwiched between the medium. Change the distance or area between the two pieces when adjusting. Its medium has air, ceramics, mica, film and so on.
Variable capacitance	It consists of a set of plates and a set of dynamic film, its capacity with the rotation of the moving film can be continuously changed. The two groups of variable capacitance are mounted in a coaxial rotation called double-connected. Variable capacitance medium has two kinds of air and polystyrene. The air medium variable capacitance is large in volume, low in loss and used in tube radios. The polystyrene medium variable capacitance is made into a sealed, small size and is used more in transistor radios.

The capacitance of the capacitor is the nominal capacity of the capacitor. The nominal capacity of the capacitor and its actual capacity will be error. Common fixed capacitance allowable error level is shown in table 2. The nominal capacity series of commonly used fixed capacitance is shown in table 3.

Table 2 Common fixed capacitance allowable error level

Allowable error	±2%±5%±10%±20% (+20%-30%)  (+50%-20%) (+100%-10%)
Level	02ⅰⅱⅲⅳⅴⅵ

Table 3 nominal capacity series of commonly used fixed capacitance

Capacitance category	Allowable error	Capacity Range	Nominal capacity Series
Paper dielectric capacitance, metallized paper dielectric capacitance, paper film composite dielectric capacitance, low frequency (polar) organic film dielectric capacitance	±5% ±10% ±20%	100pf~1uf	1.0 1.5 2.2 3.3 4.7 6.8
		1uf~100uf	1 2 4 6 8 10 15 20 30 50 60 80 100
High frequency (nonpolar) Organic film dielectric capacitance, porcelain dielectric capacitance, glass glaze capacitor, mica capacitor	±5%		1.1 1.2 1.3 1.5 1.6 1.8 2.0 2.4 2.7 3.0 3.3 3.6 3.9 4.3 4.7 5.1 5.6 6.2 6.8 7.5 8.2 9.1
	±10%		1.0 1.2 1.5 1.8 2.2 2.7 3.3 3.9 4.7 5.6 6.8 8.2
	±20%		1.0 1.5 2.2 3.3 4.7 6.8
Electrolytic capacitors for aluminum, tantalum, niobium and Titanium	±10% ±20% +50/-20% +100/-10%		1.0 1.5 2.2 3.3 4.7 6.8 (Capacity unit UF)

Capacitor long-term reliable operation, it can withstand the maximum DC voltage, is the capacitive voltage, also known as the DC operating voltage capacitor. If in the AC circuit, be aware that the added AC voltage maximum value can not exceed the DC operating voltage value of the capacitor.
Table 4 is a common fixed capacitance DC operating voltage series.  There are * values, only for electrolytic capacitors. http://hovertree.com/menu/yingjian/

Table 4 common fixed capacitance DC voltage series

1.6 4 6.3 10 16 25 32* 40 50 63 100 125* 160 250 300* 400 450* 500 630 1000

Because the dielectric between the two poles is not an absolute insulator, its resistance is not infinite, but a finite value, generally above 1000 trillion euro. The resistors between the two poles are called insulation resistors, or leakage resistors. The smaller the leakage resistance, the more serious the leakage. Capacitance leakage can cause energy loss, which affects not only the life of the capacitor, but also the work of the circuit. Therefore, the larger the leakage resistance, the better.

There are also many types of capacitors, in order to distinguish between, also commonly used in several Latin letters to indicate the type of capacitance, 2 shows. The first letter, C, represents the capacitance, the second letter represents the media material, and the third letter represents the shape, structure, and so on. The above is a small paper dielectric capacitance, the following is the vertical moment to open the sealing paper dielectric capacitance. Table 5 lists the categories and symbols for the capacitance. Table 6 is a few of the characteristics of commonly used capacitors.

                                                                |------------------------                               C: Capacitor

                                      ------------------|         c Z x             |-------------------    Z: Paper Media

|____0.022uf_____| X: Small

Figure 2

Table 5 categories and symbols for capacitors

Order	Category	Name	Hereinafter	Title
First letter	Main claim	Capacitor	Capacity	C
A second letter	Media materials	Paper Media Electrolyte Mica High Frequency Porcelain Medium Low Frequency porcelain Medium Metallized paper Medium Organic films such as polystyrene Polyester and other organic films	Paper Electric Cloud Porcelain	Z D Y C T J B L
A third letter later	Shape	Cylindrical Tube-shaped Vertical Rectangle Round sheet shape	Tube Tube State Round	T G L Y
	Structure	Seal	Dense	M
	Size	Small	Small	X

　  

Table 6 Several characteristics of common capacitance

Capacitance type	Capacity Range	DC operating voltage (V)	Frequency of Use (MHZ)	Accuracy	Leakage Resistance (MΩ)
Medium and small size paper dielectric capacitance	470pf~0.22uf	63~630	8 or less	Ⅰ~ⅲ	>5000
Metal shell sealing paper dielectric capacitance	0.01uf~10uf	250~1600	DC, pulsating DC	Ⅰ~ⅲ	>1000~5000
Medium and small metallized paper dielectric capacitance	0.01uf~0.22uf	160, 250, 400	8 or less	Ⅰ~ⅲ	>2000
Metal shell Sealed metallized paper dielectric capacitance	0.22uf~30uf	160~1600	DC, Ripple	Ⅰ~ⅲ	>30~5000
Film Capacitors	3pf~0.1uf	63~500	High frequency, low frequency	Ⅰ~ⅲ	>10000
Mica Capacitor	10pf~0.51uf	100~7000	75~250 below	02~ⅲ	>10000
Porcelain dielectric capacitance	1pf~0.1uf	63~630	Low frequency, high frequency 50~3000 below	02~ⅲ	>10000
Aluminum Electrolytic Capacitors	1uf~10000uf	4~500	DC, pulsating DC	Ⅳⅴ
Tantalum and niobium electrolytic capacitors	0.47uf~1000uf	6.3~160	Dc Pulsating DC	Ⅲⅳ
Porcelain-Medium Trimmer capacitors	2/7pf~7/25pf	250~500	High frequency		>1000~10000
Variable capacitance	Min >7PF Max <1100PF	100 or more	Low frequency, high frequency		>500

The basic unit of capacitance is: F (method) ΜF (micro-method) PF (Peel method) NF (Nano-method) We are common in general are ΜF, NF, PF units. The specific conversions between them are as follows: 1F=1,000,000UF1UF=1,000NF1NF=1000PF

① with UF as a unit: capacitance capacity of more than 1uF, directly to the number of values, such as 10000uf,3300uf.

The ② takes PF as a unit: the first and second digits represent the capacitance, and the third number represents the 10, which is the number of the 0. For example, the capacitance of the capacity is shown as 104, representing 10 behind four 0, i.e. 100000pF.

③ with NF as a unit: the capacitance capacity of the 100N represents 100x10-9=10-7 Faraday, also as 0.1x10-6 Faraday, so 0.1UF.

Note:

Usually when the capacity is less than 10000pF, use PF to do units, and with Jianne, such as 1000PF labeled 102, 10000PF labeled 103, greater than 10000pF, with UF units.

For simplicity, capacitors larger than 100pF and less than 1uF are often not unit-injected. There is no decimal point, its unit is PF, there is a decimal point, its unit is UF. For example, 3300 is 3300pF can also be 332,0.1 is 0.1uF and so on. Note: Like the Jianne is often used in PF units of capacitance, such as 1000PF is 102,100000 of course 104 (0.1uF), 3300 is 332. http://www.cnblogs.com/roucheng/

Basic knowledge of Capacitance