Introduction to capacitors What is a capacitor?
What is a capacitor? Two electrical conductors close to each other, with a non-conductive insulating layer in the middle, form a capacitor. When the working voltage is added between the two pole pieces of the capacitor, the capacitor will store positive charge. The capacitance of a capacitor is equivalent to the ratio of the amount of charge on a conductive pole piece to the working voltage between two pole pieces. The basic element of the capacitance of a capacitor is Farad (F). The English letter C is generally used to indicate capacitive components on circuit diagrams. Capacitors play a key role in circuits such as automatic tuning, bypass, coupling, and filtering. It should be used in the automatic tuning circuit of the transistor recorder, and the coupling circuit and the bypass circuit of the color TV should also use it. With the rapid development of information technology in electronic devices, the upgrading rate of digital electronic equipment has become faster and faster, and the sales volume of consumer electronic equipment led by flat-panel TVs (LCD and PDP), notebooks, digital cameras and other commodities has grown steadily , Has promoted the improvement of the capacitor industry chain. In a DC circuit, a capacitor is equivalent to a short circuit. A capacitor is a component that can store positive charges, and it is also one of the most common electronic components. The structure of the capacitor: A very simple capacitor is composed of pole pieces on both sides and an insulating layer of electrolytic medium (containing gas) in the middle. After plugging in, the pole pieces are energized and a working voltage (potential difference) is generated. However, because of the chemical substance of the insulating layer in the middle, all capacitors are not conductive. However, such a situation is under the necessary conditions that do not exceed the critical value of the capacitor's operating voltage (breakdown field strength). We know that all chemical substances are relatively insulating layers. When the working voltage on both sides of the chemical substance increases to a certain level, the chemical substances are all conductive. Everyone calls this working voltage the breakdown field strength. Capacitors are not excluded. After the capacitor is penetrated, it is not a conductor or an insulator. But in the middle school stage, such working voltage is not visible in the circuit, so it is all working under the breakdown field strength and can be seen as a conductor and an insulator. However, in a communication AC circuit, the direction of the current changes as a function of time. The whole process of charging the capacitor battery has time. At this time, a transformed electrostatic field is generated between the pole pieces, and this electrostatic field is also a factor that changes over time. In fact, the amount of current is based on the electrostatic field between the capacitors. Efficacy of capacitors: Coupling: Capacitors used in coupling circuits are called coupling capacitors. Many applications of this type of capacitor circuits are used in resistance-capacitance coupling amplifiers and other capacitor coupling circuits, which can block the flow of goods and communicate with each other. Filtering: The capacitor used in the filter circuit is called the filter capacitor. This type of capacitor circuit is used in switching power supply filters and various filter circuits. The filter capacitor removes the signal in a certain frequency range from the total signal. Decoupling: The capacitor used in the decoupling circuit is called the decoupling capacitor. This type of capacitor circuit is used in the AC voltage supply circuit of the multi-level amplifier. The decoupling capacitor removes the harmful low-frequency cross-connection in the middle of each level amplifier. High-frequency vibration suppression: The capacitor used in the high-frequency vibration suppression circuit is called high-frequency vibration suppression capacitor. In the audio frequency negative feedback amplifier, in order to better eliminate the high-frequency self-excited oscillation that is likely to occur, select This type of capacitor circuit is used to remove high-frequency noise that is likely to occur in the amplifier. Series resonance: The capacitor used in the LC series resonant circuit is called the series resonant capacitor. This type of capacitor circuit is required on both the LC parallel and series series resonant circuits. Bypass: The capacitor used in the bypass circuit is called the bypass capacitor. If the signal in a certain frequency range must be removed from the signal in the circuit, a bypass capacitor circuit can be used. Depending on the frequency of the removed signal, there are Full frequency domain (all communicating AC signals) bypass capacitor circuit and high frequency bypass capacitor circuit. Zhonghe: The capacitor used in the Zhonghe circuit is called Zhonghe capacitor. In high-frequency and high-frequency amplifiers for recorders and TV high-frequency amplifiers, this type of neutral capacitor circuit is used to eliminate self-oscillation. On-time: The capacitor used in the on-time circuit is called on-time capacitance. In the circuit that must be controlled according to the charging, charging and discharging development time of the capacitor battery, the on-time capacitor circuit is used, and the capacitor functions to manipulate the size of the steady state value. Integration: The capacitor used in the integration circuit is called the integration capacitance. In the isolating circuit of the electric potential difference field scanner, using this type of integrating capacitor circuit can remove the field sync signal from the field composite sync signal. Differentiate: The capacitor used in the differential circuit is called the differential capacitor. In order to better obtain the sharp turn-on signal in the trigger principle circuit, this type of differential capacitor circuit is selected to obtain the sharp single-pulse turn-on signal from various (mainly rectangular pulse) signals. Compensation: The capacitor used in the compensation circuit is called compensation capacitor. In the bottom sound compensation circuit of the card, this kind of low frequency compensation capacitor circuit is used to improve the low frequency signal in the playing music signal. In addition, there are also high frequencies. Compensation capacitor circuit. Bootstrap: The capacitor used in the bootstrap circuit is called the bootstrap capacitor. The common OTL power amplifier circuit output stage circuit selects this type of bootstrap capacitor circuit to slightly increase the positive self-induced electromotive force of the signal according to the feedback adjustment method. . Crossover: The capacitor in the crossover circuit is called the crossover capacitor. In the audio speaker crossover circuit, the crossover capacitor circuit is used to make the high frequency speaker work in the high frequency range, high frequency The speaker is working in the Chinese frequency range, and the low frequency speaker is working in the low frequency range. Load capacitance: refers to the reasonable external capacitance that determines the load series resonance together with the quartz crystal resonator. Common index values of load capacitance are 16pF, 20pF, 30pF, 50pF and 100pF. The load capacitance can be adjusted appropriately according to the detailed situation. According to the adjustment, the output power of the resonator can generally be adjusted to the tolerance value. Classification: According to the structure, it is divided into three categories: fixed capacitors, variable capacitors and adjustable capacitors. 2 Classified by electrolyte solution: organic chemical substance capacitors, inorganic substance capacitors, electrolytic capacitors, electric heating capacitors and gaseous substance capacitors. According to the main purpose, it is divided into: high frequency bypass, low frequency bypass, filtering, automatic tuning, high frequency coupling, low frequency coupling, small and medium capacitors. According to the different production materials, it can be divided into: ceramic dielectric capacitors, polyester cloth capacitors, electrolytic capacitors, tantalum capacitors, and excellent polypropylene capacitors. High frequency bypass: porcelain capacitors, biotite capacitors, glass film capacitors, polyester cloth capacitors, laminated glass glaze capacitors. Low frequency bypass: paper capacitors, porcelain capacitors, aluminum electrolytic capacitors, polyester cloth capacitors. Filtering: aluminum electrolytic capacitors, paper capacitors, composite paper capacitors, liquid tantalum capacitors. Automatic tuning: porcelain capacitors, biotite capacitors, glass film capacitors, polyethylene capacitors. Low coupling: paper capacitors, porcelain capacitors, aluminum electrolytic capacitors, polyester cloth capacitors, solid tantalum capacitors. Small and medium-sized capacitors: metalized paper capacitors, porcelain capacitors, aluminum electrolytic capacitors, polyethylene capacitors, solid tantalum capacitors, laminated glass glaze capacitors, metalized polyester cloth capacitors, polypropylene capacitors, biotite capacitors.