In a DC circuit, a capacitor is equivalent to an open circuit. Capacitors are components that store electrical charge and are one of the most commonly used electronic components. This has to start with the structure of the capacitor. The simplest capacitors are constructed with plates at both ends and an insulating dielectric (including air) in between. After being energized, the plates are charged to form a voltage (potential difference), but due to the insulating substance in the middle, the entire capacitor is non-conductive. However, such a situation is under the premise that the critical voltage (breakdown voltage) of the capacitor is not exceeded. We know that any substance is relatively insulating. When the voltage across the substance increases to a certain extent, the substance can conduct electricity. We call this voltage the breakdown voltage. Capacitors are no exception. After a capacitor is broken down, it is not an insulator. However, in the middle school stage, such a voltage is not seen in the circuit, so it all works below the breakdown voltage and can be regarded as an insulator. However, in an AC circuit, because the direction of the current changes as a function of time. The process of charging and discharging capacitors has time. At this time, a changing electric field is formed between the plates, and this electric field is also a function of time. In fact, current flows between capacitors in the form of an electric field. The role of capacitors: Coupling: The capacitors used in the coupling circuit are called coupling capacitors, which are widely used in resistance-capacitance coupling amplifiers and other capacitive coupling circuits to isolate DC and AC.

Filtering: The capacitor used in the filter circuit is called a filter capacitor. This capacitor circuit is used in power supply filtering 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 the decoupling capacitor, which is used in the DC voltage supply circuit of the multi-stage amplifier. The decoupling capacitor eliminates the harmful low-frequency cross-connection between each stage amplifier. High frequency vibration elimination: The capacitor used in the high frequency vibration elimination circuit is called the high frequency vibration elimination capacitor. In the audio negative feedback amplifier, in order to eliminate the high frequency self-excitation that may occur, this capacitor circuit is used to eliminate the high frequency self-excitation. High frequency whistling that may appear from the amplifier. Resonance: The capacitor used in the LC resonant circuit is called a resonant capacitor, which is required in both LC parallel and series resonant circuits.

Bypass: The capacitor used in the bypass circuit is called the bypass capacitor. If the signal in a certain frequency band needs to be removed from the signal in the circuit, the bypass capacitor circuit can be used. According to the frequency of the removed signal, there are full frequency range (All AC Signals) Bypass Capacitor Circuit and High Frequency Bypass Capacitor Circuit

●Neutralization: The capacitor used in the neutralization circuit is called the neutralization capacitor. In radio high-frequency and intermediate-frequency amplifiers, and television high-frequency amplifiers, this neutralizing capacitor circuit is used to eliminate self-excitation. ● Timing: capacitors used in timing circuits are called timing capacitors. Timing capacitor circuits are used in circuits that require time control through capacitor charging and discharging, and capacitors play a role in controlling the size of the time constant. ●Integration: The capacitor used in the integrating circuit is called the integrating capacitor. In the synchronizing separation circuit of potential field scanning, using this integrating capacitor circuit, the field synchronizing signal can be taken out from the field composite synchronizing signal

Differential: The capacitor used in the differential circuit is called the differential capacitor. In order to obtain the peak trigger signal in the trigger circuit, this differential capacitor circuit is used to obtain the peak pulse trigger signal from various (mainly rectangular pulse) signals. 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 are also high-frequency compensation capacitors. circuit. ● Bootstrap: The capacitor used in the bootstrap circuit is called the bootstrap capacitor. The commonly used OTL power amplifier output stage circuit adopts this bootstrap capacitor circuit to increase the positive half-cycle amplitude of the signal by a small amount of positive feedback. Frequency division: The capacitor in the frequency division circuit is called the frequency division capacitor. In the speaker frequency division circuit of the speaker, the frequency division capacitor circuit is used, so that the high frequency speaker works in the high frequency band, the intermediate frequency speaker works in the middle frequency band, and the low frequency speaker works in the low frequency band. Loudspeakers work in low frequency

●Load capacitance: refers to the effective external capacitance that determines the load resonance frequency together with the quartz crystal resonator. Commonly used standard values ​​for load capacitance are 16pF, 20pF, 30pF, 50pF and 100pF. The load capacitance can be adjusted appropriately according to the specific situation, and the operating frequency of the resonator can generally be adjusted to the nominal value through adjustment.