Capacitor is an electronic component widely used in electronic equipment, widely used in DC blocking, coupling, bypass, filtering, tuning loop, energy conversion, control and other aspects in the circuit.
In a DC circuit, a capacitor is equivalent to an open circuit. A capacitor is a component that can store charge and is one of the most commonly used electronic components.Capacitor is an electronic component widely used in electronic equipment, widely used in DC blocking, coupling, bypass, filtering, tuning loop, energy conversion, control and other aspects in the circuit. Do you know about the role of capacitors?
The simplest capacitor consists of plates at both ends and an insulating dielectric (including air) in between. After electrification, the plates are charged to form a voltage (potential difference), but due to the insulating material 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 level, the substance can conduct electricity. We call this voltage the breakdown voltage. Capacitors are no exception. After a capacitor is broken down, it is no longer an insulator. However, in the middle school stage, such voltage is not seen in the circuit, so they all work below the breakdown voltage and can be regarded as an insulator.
However, in an AC circuit, the direction of the current changes as a function of time. The process of charging and discharging the capacitor has time. At this time, a changing electric field is formed between the plates, and this electric field is also a function of changing with time. In fact, the current is passed between the capacitors in the form of an electric field.
The basic working principle of the capacitor is charging and discharging, and of course rectification, oscillation and other functions. In addition, the structure of the capacitor is very simple, mainly composed of two positive and negative electrodes and an insulating medium sandwiched between them, so the capacitor type is mainly composed of electrodes and the insulating medium. There are many uses of capacitors, mainly as follows:
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The role of capacitors:
●Coupling: Capacitors used in coupling circuits are called coupling capacitors, which are widely used in RC coupling amplifiers and other capacitive coupling circuits to block DC and AC.
Filtering: The capacitor used in the filter circuit is called a filter capacitor. This capacitor circuit is used in power filtering and various filter circuits. The filter capacitor removes signals in a certain frequency band from the total signal.
●Decoupling: The capacitor used in the decoupling circuit is called a decoupling capacitor. This capacitor circuit is used in the DC voltage supply circuit of a multi-stage amplifier. The decoupling capacitor eliminates the harmful low-frequency cross-connection between each amplifier.
●High-frequency vibration elimination: The capacitor used in the high-frequency vibration elimination circuit is called a 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 Possible high-frequency howling of 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 a bypass capacitor. If you need to remove a certain frequency band signal from the signal in the circuit, you can use a bypass capacitor circuit. According to the frequency of the signal to be removed, 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 capacitance. In radio high-frequency and intermediate frequency amplifiers, and TV high-frequency amplifiers, this neutralization capacitor circuit is used to eliminate self-excitation.
●Timing: The capacitors used in timing circuits are called timing capacitors. A timing capacitor circuit is used in a circuit that requires time control through capacitor charging and discharging, and the capacitor plays a role in controlling the time constant.
●Integral: The capacitor used in the integral circuit is called integral capacitance. In the synchronous separation circuit of potential field scanning, the field synchronous signal can be taken out from the field compound synchronous signal by adopting this integral capacitance circuit.
● Differential: The capacitor used in the differential circuit is called differential capacitance. In order to obtain the peak trigger signal in the trigger circuit, this differential capacitance 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 a 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.
●Bootstrap: The capacitor used in the bootstrap circuit is called a bootstrap capacitor. The commonly used OTL power amplifier output stage circuit uses this bootstrap capacitor circuit to slightly increase the positive half-cycle amplitude of the signal through positive feedback.
Frequency division: The capacitor in the frequency division circuit is called a frequency division capacitor. In the speaker frequency division circuit of the speaker, a frequency division capacitor circuit is used to make the high frequency speaker work in the high frequency band, the intermediate frequency speaker in the middle frequency band, and the low frequency The speakers work in the low frequency range.
●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. Generally, the operating frequency of the resonator can be adjusted to the nominal value by adjustment.