為什么電路中要有電容？就要從
電容在電路中的作用說起：電容是容納和釋放電荷的電子元器件。電容的基本工作原理就是充電放電，還有整流、振蕩及其它作用。另外電容的結構非常簡單，主要由兩塊正負電極和夾在中間的絕緣介質組成，所以電容類型主要是由電極和絕緣介質決定的。
Why is there a capacitor in the circuit? Let's start from the role of capacitors in the circuit: capacitors are electronic components that hold and release electric charges. The basic working principle of capacitor is charging and discharging, as well as rectification, oscillation and other functions. In addition, the structure of capacitor is very simple, which is mainly composed of two positive and negative electrodes and insulating medium sandwiched in the middle. Therefore, the type of capacitor is mainly determined by the electrode and insulating medium.
雖然電容的體積很小，但并不影響其在電路中的重要作用。接下來，就讓我們一起來盤點一下電容在電路中的27種作用。
Although the volume of capacitance is very small, it does not affect its important role in the circuit. Next, let's check the 27 functions of capacitors in the circuit.
1、濾波電容
Filter capacitor
濾波電容接在直流電壓的正負極之間，以濾除直流電源中不需要的交流成分，使直流電平滑，通常采用大容量的電解電容，也可以在電路中同時并接其它類型的小容量電容以濾除高頻交流電。
The filter capacitor is connected between the positive and negative poles of the DC voltage to filter out the unwanted AC components in the DC power supply and make the DC level slip. Usually, large capacity electrolytic capacitors are used, or other types of small capacity capacitors can be connected in parallel in the circuit to filter out high-frequency AC current.
2、退耦電容
Decoupling capacitor
退耦電容并接于放大電路的電源正負極之間，防止由電源內阻形成的正反饋而引起的寄生振蕩。
The decoupling capacitor is connected in parallel between the positive and negative poles of the power supply of the amplifier circuit to prevent parasitic oscillation caused by the positive feedback formed by the internal resistance of the power supply.
3、旁路電容
Bypass capacitance
在交直流信號的電路中，將電容并接在電阻兩端或由電路的某點跨接到公共電位上，為交流信號或脈沖信號設置一條通路，避免交流信號成分因通過電阻產生壓降衰減。
In the circuit of AC and DC signals, the capacitance is connected to both ends of the resistance in parallel or connected to the common potential from a point of the circuit, and a path is set for the AC signal or pulse signal to avoid the voltage drop attenuation of the AC signal components due to resistance.
4、耦合電容
Coupling capacitance
在交流信號處理電路中，用于連接信號源和信號處理電路或者作為兩放大器的級間連接,用于隔斷直流，讓交流信號或脈沖信號通過，使前后級放大電路的直流工作點互不影響。
In the AC signal processing circuit, it is used to connect the signal source and the signal processing circuit or as the interstage connection of two amplifiers, to isolate the DC, let the AC signal or pulse signal pass through, so that the DC working points of the front and rear amplifier circuits do not affect each other.
5、調諧電容
Tuning capacitor
連接在諧振電路的振蕩線圈兩端，起到選擇振蕩頻率的作用。
It is connected at both ends of the oscillating coil of the resonant circuit to select the oscillating frequency.
6、襯墊電容
Pad capacitance
它與諧振電路主電容串聯的輔助性電容，調整它可使振蕩信號頻率范圍變小，并能顯著地提高低頻端的振蕩頻率。
It is an auxiliary capacitor connected in series with the main capacitor of the resonant circuit. By adjusting it, the frequency range of the oscillating signal can be reduced, and the oscillating frequency at the low frequency end can be significantly increased.
7、補償電容
Compensation capacitance
補償電容與諧振電路主電容并聯的輔助性電容，調整該電容能使振蕩信號頻率范圍擴大。
The compensation capacitor is an auxiliary capacitor in parallel with the main capacitor of the resonant circuit. Adjusting the capacitor can expand the frequency range of the oscillating signal.
8、中和電容
Neutralizing capacitance
并接在三極管放大器的基極與發射極之間，構成負反饋網絡，以抑制三極管極間電容造成的自激振蕩。
It is connected in parallel between the base and emitter of the triode amplifier to form a negative feedback network to suppress the self-excited oscillation caused by the interelectrode capacitance of the triode amplifier.
9、穩頻電容
Frequency stabilizing capacitor
在振蕩電路中，起穩定振蕩頻率的作用。
In the oscillation circuit, it plays a role in stabilizing the oscillation frequency.
10、定時電容
Timing capacitor
在RC時間常數電路中與電阻R串聯，共同決定充放電時間長短的電容。
The capacitance that is connected in series with the resistor R in the RC time constant circuit to jointly determine the charging and discharging time.
11、加速電容
Accelerating capacitor
接在振蕩器反饋電路中，使正反饋過程加速，提高振蕩信號的幅度。
It is connected to the feedback circuit of the oscillator to accelerate the positive feedback process and improve the amplitude of the oscillation signal.
12、縮短電容
Shorten capacitance
在UHF高頻頭電路中，為了縮短振蕩電感器長度而串聯的電容。
In a UHF tuner circuit, a capacitor connected in series to shorten the length of the oscillating inductor.
13、克拉波電容
Crabbe capacitance
在電容三點式振蕩電路中，與電感振蕩線圈串聯的電容，起到消除晶體管結電容對頻率穩定性影響的作用。
In the capacitance three-point oscillation circuit, the capacitance in series with the inductance oscillation coil plays a role in eliminating the influence of the transistor junction capacitance on the frequency stability.
14、錫拉電容
Scylla capacitor
在電容三點式振蕩電路中，與電感振蕩線圈兩端并聯的電容，起到消除晶體管結電容的影響，使振蕩器在高頻端容易起振。
In the capacitor three-point oscillation circuit, the capacitance in parallel with both ends of the inductance oscillation coil can eliminate the influence of the transistor junction capacitance, making the oscillator easy to start oscillation at the high-frequency end.
15、穩幅電容
Amplitude stabilizing capacitance
在鑒頻器中，用于穩定輸出信號的幅度。
In the frequency discriminator, it is used to stabilize the amplitude of the output signal.
16、預加重電容
Preemphasis capacitor
為了避免音頻調制信號在處理過程中造成對分頻量衰減和丟失，而設置的RC高頻分量提升網絡電容。
In order to avoid the attenuation and loss of the frequency divider during the processing of the audio modulation signal, the RC high-frequency component is set to enhance the network capacitance.
17、去加重電容
De weighting capacitor
為了恢復原伴音信號，要求對音頻信號中經預加重所提升的高頻分量和噪聲一起衰減掉，設置RC在網絡中的電容。
In order to recover the original accompanying sound signal, it is required to attenuate the high frequency component and noise in the audio signal that are enhanced by pre emphasis together, and set the RC capacitance in the network.
18、移相電容
Phase-shifting capacitor
移相電容用于改變交流信號相位的電容。
The capacitance used to change the phase of an AC signal.
19、反饋電容
Feedback capacitor
跨接于放大器的輸入與輸出端之間，使輸出信號回輸到輸入端的電容。
The capacitance that spans between the input and output terminals of the amplifier, so that the output signal is returned to the input terminal.
20、降壓限流電容
Step down current limiting capacitor
串聯在交流回路中，利用電容對交流電的容抗特性，對交流電進行限流，從而構成分壓電路。
It is connected in series in the AC circuit, and uses the capacitive reactance characteristics of capacitors to limit the current of AC, thus forming a voltage divider circuit.
21、逆程電容
Reverse capacitance
用于行掃描輸出電路，并接在行輸出管的集電極與發射極之間，以產生高壓行掃描鋸齒波逆程脈沖，其耐壓一般在1500伏以上。
It is used for line scanning output circuit and connected between collector and emitter of line output tube to generate high-voltage line scanning sawtooth wave reverse pulse. Its withstand voltage is generally above 1500 V.
22、S校正電容
S correction capacitance
串接在偏轉線圈回路中，用于校正顯像管邊緣的延伸線性失真。
It is connected in series in the deflection coil circuit to correct the extended linear distortion of the picture tube edge.
23、自舉升壓電容
Bootstrap boost capacitor
利用電容器的充、放電儲能特性提升電路某點的電位,使該點電位達到供電端電壓值的2倍。
Use the charging and discharging energy storage characteristics of the capacitor to increase the potential of a point in the circuit, so that the potential of the point is twice the voltage value of the power supply terminal.
24、消亮點電容
Anti bright point capacitor
設置在視放電路中，用于關機時消除顯像管上殘余亮點的電容。
The capacitor is arranged in the video amplifier circuit to eliminate the residual bright spots on the picture tube when it is turned off.
25、軟啟動電容
Soft start capacitor
一般接在開關電源的開關管基極上，防止在開啟電源時，過大的浪涌電流或過高的峰值電壓加到開關管基極上，導致開關管損壞。
It is generally connected to the switch tube base of the switching power supply to prevent the switch tube from being damaged when excessive surge current or excessive peak voltage is applied to the switch tube base when the power supply is turned on.
26、啟動電容
Starting capacitance
串接在單相電動機的副繞組上，為電動機提供啟動移相交流電壓，在電動機正常運轉后與副繞組斷開。
It is connected to the secondary winding of single-phase motor in series to provide the motor with starting phase-shifting AC voltage, and is disconnected from the secondary winding after the motor operates normally.
27、運轉電容
Operating capacitance
與單相電動機的副繞組串聯，為電動機副繞組提供移相交流電流。在電動機正常運行時，與副繞組保持串接。
It is connected in series with the secondary winding of single-phase motor to provide phase-shifting AC current for the secondary winding of motor. When the motor operates normally, it shall be connected in series with the auxiliary winding.
綜上就是電容器在電路中的作用，雖說小小的電容器看起來很不起眼，但是在電路中卻發揮著非常重要的作用，選擇適合的電容器發揮其作用才能體現其最優的價值。
To sum up, it is the role of capacitors in the circuit. Although small capacitors look inconspicuous, they play a very important role in the circuit. Only by selecting suitable capacitors to play their role can their optimal value be reflected.
