Capacitors are components that store electricity and electrical energy (potential energy). A conductor is surrounded by another conductor, or the electric field lines emitted by one conductor all terminate in the conduction system of the other conductor, which is called a capacitor.
Two adjacent conductors are sandwiched by a layer of non-conductive insulating medium to form a capacitor. When a voltage is applied between two plates of a capacitor, the capacitor stores charge. The capacitance of a capacitor is numerically equal to the ratio of the amount of charge on one conductive electrode plate to the voltage between two electrode plates. The basic unit of capacitance of a capacitor is a farad. The capacitor element is usually represented by the letter C in the circuit diagram.
Capacitors play an important role in circuits such as tuning, bypassing, coupling, and filtering. It is used in the tuning circuit of the transistor radio, and it is also used in the coupling circuit and bypass circuit of the color TV.
1. Divided into three categories according to structure: fixed capacitors, variable capacitors and trimmer capacitors.
2. Classified by electrolyte: organic dielectric capacitors, inorganic dielectric capacitors, electrolytic capacitors, electric heating 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 capacitors.
4． It can be divided into ceramic capacitors, polyester capacitors, electrolytic capacitors, tantalum capacitors, and advanced polypropylene capacitors.
5． High-frequency bypass: ceramic capacitors, mica capacitors, glass film capacitors, polyester capacitors, glass glaze capacitors.
6. Low frequency bypass: paper dielectric capacitors, ceramic capacitors, aluminum electrolytic capacitors, polyester capacitors.
7, filtering: aluminum electrolytic capacitors, paper capacitors, composite paper capacitors, liquid tantalum capacitors.
8. Tuning: ceramic capacitors, mica capacitors, glass film capacitors, polystyrene capacitors.
9. Low coupling: paper dielectric 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.
● Coupling: The capacitor used in the coupling circuit is called coupling capacitor. It is widely used in resistance-capacitance coupling amplifiers and other capacitive coupling circuits to block DC and AC.
● Filter: The capacitor used in the filter circuit is called filter capacitor. This capacitor circuit is used in power supply filter and various filter circuits. The filter capacitor removes the signal in a certain frequency band from the total signal.
Decoupling: The capacitor used in the decoupling circuit is called decoupling capacitor. This capacitor circuit is used in the DC voltage supply circuit of the multi-stage amplifier. The decoupling capacitor eliminates harmful low-frequency cross-links between each stage of the amplifier.
● High frequency vibration damping: The capacitor used in high frequency vibration damping circuit is called high frequency vibration damping capacitor. In the audio negative feedback amplifier, in order to suppress the high frequency self-excitation that may occur, this capacitor circuit is used to eliminate High frequency howling may occur in the amplifier.
● Resonance: The capacitor used in the LC resonance circuit is called resonance capacitance. This type of capacitor circuit is required in both LC parallel and series resonance circuits.
● Bypass: The capacitor used in the bypass circuit is called the bypass capacitor. If a certain frequency band signal needs to be removed from the signal in the circuit, a bypass capacitor circuit can be used. Depending on the frequency of the removed signal, there is a full frequency domain. (All AC signals) Bypass capacitor circuit and high-frequency bypass capacitor circuit.
● Neutralization: The capacitor used in the neutralization circuit is called neutralization capacitor. In radio high-frequency and intermediate-frequency amplifiers and television high-frequency amplifiers, such a neutralizing capacitor circuit is used to eliminate self-excitation.
● Timing: The capacitor used in the timing circuit is called timing capacitance. The timing capacitor circuit is used in the circuit that needs time control through capacitor charging and discharging. The capacitor plays a role in controlling the size of the time constant.
● Integration: The capacitor used in the integration circuit is called integration capacitance. In the synchronous separation circuit of potential field scanning, using this integrating capacitor circuit, the field synchronization signal can be taken out from the field composite synchronization signal.
● Differential: The capacitor used in the differential circuit is called differential capacitance. In order to get the sharp trigger signal in the trigger circuit, this differential capacitor circuit is used to get the sharp pulse trigger signal from various types of signals (mainly rectangular pulses).
● Compensation: The capacitor used in the compensation circuit is called compensation capacitor. In the bass compensation circuit of the deck, this low-frequency compensation capacitor circuit is used to enhance the low-frequency signal in the playback signal. In addition, there is a high-frequency compensation capacitor. Circuit.
● Boost: The capacitor used in the bootstrap circuit is called the bootstrap capacitor. The commonly used OTL power amplifier output stage circuit uses this bootstrap capacitor circuit to increase the positive half-cycle amplitude of the signal by a small amount through positive feedback.
● Frequency division: The capacitor in the frequency division circuit is called frequency division capacitor. In the speaker frequency division circuit of the speaker, the frequency division capacitor circuit is used to make the high frequency speaker work in the high frequency band, the intermediate frequency speaker works in the middle frequency band, and the low frequency The speakers work in the low frequency band.
● Load capacitance: It means the effective external capacitance that determines the resonance frequency of the load together with the quartz crystal resonator.