What is a capacitor?
Capacitor, also known as "capacitance", refers to the storage of free charge under a given potential difference, which is recorded as C, and the international unit is farad (f). Generally speaking, the charge will move under force in the electric field. When there is a medium between the conductors, it hinders the charge movement and makes the charge accumulate on the conductor, resulting in the cumulative storage of charge. The amount of stored charge is called capacitance. conformal-coated tantalum capacitors
Capacitance is the ability to hold charge. Any electrostatic field is composed of many capacitors. If there is an electrostatic field, there is a capacitance. Capacitance is described by electrostatic field. It is generally believed that an isolated conductor forms a capacitance with infinity, and the conductor grounding is equivalent to being connected to infinity and connected with the earth as a whole.HVAC capacitors
Capacitance (or electrical capacity) is a physical quantity that shows the ability of a capacitor to hold charge. Physically speaking, capacitance is a static charge storage medium, which may exist permanently. This is its characteristic. It has a wide range of uses. It is an indispensable electronic component in the field of electronics and power. It is mainly used in power filtering, signal filtering, signal coupling, resonance, filtering, compensation, charge and discharge, energy storage, DC isolation and other circuits.power film capacitors
Calculation formula of capacitance:
For a capacitor, if the potential difference between the two stages is 1 volt with 1 Bank of electricity, the capacitance of the capacitor is 1 farad, that is, C = q / u. However, the capacitance is not determined by Q (charge) or u (voltage), that is, the determination formula of capacitance is: C= ε rS/4πkd 。 Among them, ε R is the relative dielectric constant, s is the positive area of the capacitor plate, D is the distance between the capacitor plates, and K is the electrostatic constant. Common parallel plate capacitor, the capacitance is C= ε S/d（ ε Is the dielectric constant of the medium between the plates, ε=ε r ε 0 ε 0 = 1 / 4 π K, s is the area of the plates, D is the distance between the plates).
Definition:
Calculation formula of electric potential energy of capacitor: e = C * (u ^ 2) / 2 = Qu / 2 = (Q ^ 2) / 2C
Calculation formula for parallel connection of multiple capacitors: C = C1 + C2 + C3 +... + CN
Multi capacitor series calculation formula: 1 / C = 1 / C1 + 1 / C2 +... + 1 / cn
Three capacitors in series: C = (C1 * C2 * C3) / (C1 * C2 + C2 * C3 + C1 * C3)
Type of capacitor:
The types of capacitors can be divided into: non-polar variable capacitor, non-polar fixed capacitor, polar capacitor, etc. in principle, they can be divided into: CBB capacitor (polyethylene), polyester capacitor, ceramic chip capacitor, mica capacitor, monolith capacitor, electrolytic capacitor, tantalum capacitor, etc.multilayer ceramic capacitors Nonpolar variable capacitor
Manufacturing process: the rotatable moving piece is a ceramic piece, the surface is plated with metal film, and the fixed piece is a ceramic bottom plated with metal film; The moving sheet is a coaxial metal sheet, and the fixed sheet is an organic film sheet as the medium
Advantages: easy production and low technical content.
Disadvantages: large volume and small capacity
Purpose: to change the oscillation and resonance frequency circuit. FM, am, transmit / receive circuit
Nonpolar inductive CBB capacitor
Manufacturing process: two layers of polypropylene plastic and two layers of metal foil are mixed alternately and then bound.
Advantages: no inductance, good high frequency characteristics and small volume
Disadvantages: not suitable for large capacity, high price and poor heat resistance.
Purpose: coupling / oscillation, audio, analog / digital circuit, high frequency power supply, filtering / decoupling ,Nonpolar CBB capacitor
Manufacturing process: two layers of polyethylene plastic and two layers of metal foil are mixed alternately and then bound.
Nonpolar porcelain capacitor
Manufacturing process: the thin porcelain piece is made by crossing metal film silver on both sides.
Advantages: small size, high withstand voltage, low price and high frequency (one is high frequency capacitor)
Disadvantages: fragile, low capacity
Purpose: high frequency oscillation, resonance, decoupling, sound
Nonpolar mica capacitor
Manufacturing process: two layers of metal films are plated on mica sheet
Advantages: easy production and low technical content.
Disadvantages: large volume and small capacity. Purpose: oscillation, resonance, decoupling and circuit with low requirements. The volume of non-polar single stone capacitor is smaller than CBB. Others are the same as CBB
Purpose: analog / digital circuit, signal bypass / filtering, audio
Polar electrolytic capacitor
Manufacturing process: two pieces of aluminum strips and two layers of insulating films are stacked with each other, and then immersed in electrolyte after being bundled.
Advantages: large capacity.
Disadvantages: poor high frequency characteristics.
Purpose: low frequency inter stage coupling, bypass, decoupling, power filter, audio
Tantalum capacitor
Manufacturing process: use metal tantalum as the positive electrode and spray metal outside the electrolyte as the negative electrode.aluminum electrolytic capacitors
Advantages: good stability, large capacity and good high frequency characteristics.
Disadvantages: high cost.
Application: high precision power filter, signal stage coupling, high frequency circuit, audio circuit
Polyester (polyester) capacitor
Symbols: CL
Capacitance: 40p--4u
Rated voltage: 63 -- 630V
Main features: small volume, large capacity, heat and moisture resistance, poor stability
Application: low frequency circuit with low requirements for stability and loss
polystyrene capacitor
Symbol: CB
Capacitance: 10p--1u
Rated voltage: 100V -- 30KV
Main features: stable, low loss, large volume
Application: circuit requiring high stability and loss
Polypropylene capacitor
Symbol: CBB
Capacitance: 1000p -- 10u
Rated voltage: 63 -- 2000V
Main features: the performance is similar to that of polystyrene, but the volume is small and the stability is slightly poor
Application: instead of most polystyrene or mica capacitors, it is used in circuits with high requirements
Mica capacitor
Symbols: CY
Capacitance: 10p -- 0.1U
Rated voltage: 100V -- 7kv
Main features: high stability, high reliability and small temperature coefficient
Application: high frequency oscillation, pulse and other circuits with high requirements
High frequency ceramic capacitor
Symbols: CC
Capacitance: 1 -- 6800p
Rated voltage: 63 -- 500V
Main features: low high frequency loss and good stability
Application: high frequency circuit
Low frequency ceramic capacitor
Symbols: CT
Capacitance: 10p -- 4.7u
Rated voltage: 50V -- 100V
Main features: small size, low price, large loss and poor stability
Application: low frequency circuit with low requirements
Glass glaze capacitor
Symbols: CI
Capacitance: 10p -- 0.1U
Rated voltage: 63-400v
Main features: good stability, low loss, high temperature resistance (200 ℃)
Application: pulse, coupling, bypass circuit, etc
Aluminum electrolytic capacitor
Symbols: CD
Capacitance: 0.47 -- 10000U
Rated voltage: 6.3 -- 450V
Main features: small volume, large capacity, large loss and large leakage
Applications: power filtering, low frequency coupling, decoupling, bypass, etc
Tantalum electrolytic capacitor (CA), niobium electrolytic capacitor (CN)
Capacitance: 0.1 -- 1000u
Rated voltage: 6.3 -- 125V
Main features: the loss and leakage are less than that of aluminum electrolytic capacitor
Application: replace aluminum electrolytic capacitor in circuits with high requirements
Air dielectric variable capacitor
Variable electric capacity: 100 -- 1500p
Main features: low loss and high efficiency; It can be made into linear type, linear wavelength type, linear frequency type and logarithmic type according to requirements
Applications: electronic instruments, radio and television equipment, etc
Thin film dielectric variable capacitor
Variable electric capacity: 15 -- 550p
Main features: small volume, light weight; The loss is greater than that of air medium
Application: communication, broadcast receiver, etc
Thin film dielectric trimming capacitor
Symbol: variable electric capacity: 1 -- 29p
Main features: large loss and small volume
Application: recorder, electronic instrument and other circuits for circuit compensation
Ceramic dielectric trimmer capacitor
Symbol: variable electric capacity: 0.3 -- 22P
Main features: small loss and small volume
Application: precision tuned high frequency oscillation circuit
