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The Roles of the Different Capacitors

by: Mar 12,2020 106 Views 0 Comments Posted in PCB Basic Information

Resisitor DC AC Capacitor

Capacitors are almost indispensable energy storage elements in electronic circuits. They have the characteristics of blocking DC, connecting AC, and preventing low frequency. Widely used in the coupling, blocking, bypass, filtering, tuning, energy conversion and automatic control circuits. Being familiar with the meaning of capacitor names in different circuits will help us understand electronic circuit diagrams.

1. Filter capacitor: It is connected between the positive and negative poles of the DC power supply to filter out the unnecessary AC components in the DC power supply and smooth the DC power. Generally, a large-capacity electrolytic capacitor is often used, and other types of small-capacitance capacitors can also be connected in the circuit at the same time to filter out high-frequency alternating current.

2. Decoupling capacitor: It is connected between the positive and negative poles of the power supply of the amplifier circuit in parallel to prevent parasitic oscillation caused by positive feedback formed by the internal resistance of the power supply.

3. Bypass capacitor: In the circuit of AC and DC signals, connect the capacitor in parallel at both ends of the resistor or jump to a common potential from a point in the circuit to set a path for AC signals or pulse signals to avoid AC signal components attenuation due to voltage drop through resistance.

4. Coupling capacitor: In the AC signal processing circuit, it is used to connect the signal source and the signal processing circuit or to make the inter-stage connection of the two amplifiers to cut off the DC and let the AC signal or pulse signal pass through, so that the DC operating points of the amplifying circuit before and after the stage do not affect each other.

5. Tuning capacitor: It is connected to the two ends of the oscillating coil of the resonance circuit and plays the role of selecting the oscillating frequency.

6. Pad capacitor: An auxiliary capacitor connected in series with the main capacitor of the resonance circuit. Adjusting it can make the frequency range of the oscillation signal smaller and significantly increase the oscillation frequency at the low frequency. By properly selecting the capacitance of the pad capacitor, the low-end frequency curve can be raised upward, which is close to the ideal frequency tracking curve.

7. Compensation capacitor: It is an auxiliary capacitor in parallel with the main capacitor of the resonance circuit. Adjusting this capacitor can expand the frequency range of the oscillation signal.

8. Neutralizing capacitor: It 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.

9. Frequency stabilization capacitor: In the oscillation circuit, it plays the role of stabilizing the oscillation frequency.

10. Timing capacitor: A capacitor that is connected in series with the resistor R in the RC time constant circuit to determine the length of the charge and discharge time.

11. Acceleration capacitor: It is connected in the oscillator feedback circuit to accelerate the positive feedback process and increase the amplitude of the oscillation signal.

12. Shortening capacitor: In the UHF tuner circuit, a capacitor connected in series to shorten the length of the oscillating inductor.

13. Carat capacitor: In the capacitor three-point oscillation circuit, the capacitor connected in series with the inductor oscillating coil plays a role in eliminating the influence of the transistor junction capacitance on the frequency stability.

14. Thira capacitor: In a capacitor three-point oscillation circuit, a capacitor connected in parallel with both ends of the inductive oscillating coil eliminates the influence of the transistor junction capacitance and makes the oscillator easy to start at the high-frequency end.

15. Amplitude stabilization capacitor: It is used in the frequency discriminator to stabilize the amplitude of the output signal.

16. Pre-emphasis capacitor: In order to avoid the attenuation and loss of the frequency division during the processing of the audio modulation signal, the RC high-frequency component is set to increase the network capacitance.

17. De-emphasis capacitor: In order to restore the original sound signal, it is required to attenuate the high-frequency components that have been boosted by the pre-emphasis along with the noise, and set the capacitor in the RC network.

18. Phase-shifting capacitor: The capacitor used to change the phase of the AC signal.

19. Feedback Capacitor: A capacitor that is connected between the input and output of the amplifier to return the output signal to the input.

20. Step-down current-limiting capacitor: It is connected in series in the AC power circuit. The capacitive reactance characteristic of the AC power is used to limit the AC current, thereby forming a voltage-dividing circuit.

21. Flyback capacitor: It is used for the line scan output circuit and connected between the collector and emitter of the line output tube to generate high voltage line scan sawtooth wave backhaul pulses, and its withstand voltage is generally above 1500V.

22. Correction capacitor: It is connected in series in the deflection coil circuit, used to correct the extended linear distortion at the edge of the picture tube.

23. Bootstrap boost capacitor: The charge and discharge energy storage characteristics of the capacitor are used to increase the potential at a certain point of the circuit so that the potential at this point reaches twice the voltage value of the power supply terminal.

24. Brightening point capacitor: A capacitor set in the video amplifier circuit to eliminate the residual bright point on the picture tube when the power is off.

25. Soft-start capacitor: Generally connected to the base of the switching tube of the switching power supply to prevent excessive surge current or excessive peak voltage from being added to the base of the switching tube when the power is turned on, resulting in damage to the switching tube.

26. Starting capacitor: It is connected in series to the secondary winding of a single-phase motor to provide the starting phase-shifting AC voltage for the motor. Disconnect from the secondary winding after the motor is running normally.

27. Running capacitor: It is connected in series with the secondary winding of a single-phase motor to provide phase-shifted AC current to the secondary winding of the motor. When the motor is running normally, it is connected in series with the secondary winding.

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