Capacitors are almost indispensable energy storage elements in electronic circuits. It has the characteristics of blocking DC, connecting AC, and preventing low frequencies. Widely used in coupling, DC blocking, bypass, filtering, tuning, energy conversion and automatic control circuits. Familiarity with the meaning of capacitors in different circuits will help us understand electronic circuit diagrams.
1. Filter capacitor: Connect between the positive and negative poles of the DC power supply to filter out the AC components that are not needed in the DC power supply and smooth the DC power.
Generally, large-capacity electrolytic capacitors or tantalum capacitors are used, and other types of small-capacity capacitors can also be connected in parallel to filter out high-frequency alternating current.
2. Decoupling capacitor: Connected between the positive and negative poles of the power supply of the amplifier circuit to prevent the parasitic oscillation caused by the positive feedback formed by the internal resistance of the power supply.
3. Coupling capacitor: connected in the AC signal processing circuit, used to connect the signal source and the signal processing circuit or as the inter-stage connection of two amplifiers, to cut off the DC, let the AC signal or pulse signal pass, so that the front and back stage amplifier circuit The DC operating point does not affect each other.
4. Bypass capacitor: connect to the circuit of AC and DC signals, connect the capacitor in parallel at both ends of the resistor or jump to the common potential from a certain point of the circuit, set a path for AC signal or pulse signal to avoid AC signal The component is attenuated by the voltage drop caused by the resistance.
5. Tuning capacitor: connected at both ends of the oscillating coil of the resonant circuit, it plays the role of selecting the oscillating frequency.
6. Pad capacitor and resonance capacitor: auxiliary capacitor connected in series with the main capacitor. Adjusting it can make the oscillation signal frequency range smaller, and can significantly increase the oscillation frequency at the low frequency end.
It is the capacity of the local selected pad capacitor, which can raise the low-end frequency curve upward, close to the ideal frequency tracking curve.
7. Compensation capacitor: auxiliary capacitor connected in parallel with the main capacitor of the resonant circuit. Adjusting this capacitor can expand the frequency range of the oscillation signal.
8. Neutralizing capacitor: connected in parallel between the base and emitter of the triode amplifier to form a negative feedback network to suppress the self-oscillation caused by the capacitance between the triodes.
9. Frequency stabilizing capacitor: It plays a role in stabilizing the oscillation frequency in the oscillation circuit.
10. Timing capacitor: It is connected in series with the resistor R in the RC time constant circuit to determine the capacitance of the charging and discharging time.
11. Acceleration capacitor: Connected to the oscillator feedback circuit to accelerate the positive feedback process and increase the amplitude of the oscillation signal.
12. Shorten the capacitance: In the UHF high frequency head circuit, the capacitor connected in series in order 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 inductive oscillation coil plays a role in eliminating the influence of the junction capacitance of the transistor on the frequency stability.
14. Thira capacitor: In the capacitor three-point oscillation circuit, the capacitor connected in parallel with the two ends of the inductive oscillation coil eliminates the influence of the junction capacitance of the transistor, making the oscillator easy to start vibration at the high frequency end.
15. Amplitude stabilizing capacitor: used in 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 value caused by the audio modulation signal during processing, the RC high-frequency component set enhances the network capacitance.
17. De-emphasis capacitor: In order to restore the original sound signal, it is required to attenuate the high-frequency component and noise raised by the pre-emphasis in the audio signal, and set the capacitor in the RC network.
18. Phase-shifting capacitor: a capacitor used to change the phase of an AC signal.
19. Feedback capacitance: Capacitance connected across the input and output of the amplifier to return the output signal to the input.
The name and meaning of capacitors in different circuits
20. Step-down and current-limiting capacitor: Connected in series in the alternating current circuit, using the capacitive reactance characteristic of the capacitor to the alternating current to limit the alternating current, thereby forming a voltage divider circuit.
21. Reverse capacitance: used in the line scan output circuit, and connected between the collector and the emitter of the line output tube to generate a high voltage line scan sawtooth wave reverse pulse, the withstand voltage is generally above 1500V.
22. Correction capacitor: connected in series in the deflection coil circuit, used to correct the extended linear distortion at the edge of the kinescope.
The name and meaning of capacitors in different circuits
23. Bootstrap boost capacitor: Use the charging and discharging energy storage characteristics of the capacitor to increase the potential of a certain point of the circuit, so that the potential of this point reaches twice the voltage value of the power supply terminal.
24. Capacitance for eliminating bright spots: It is set in the video playback circuit and is used to eliminate the residual bright spots on the picture tube during shutdown.
25. Soft-start capacitor: It is generally connected to the base of the switch tube of the switching power supply to prevent excessive surge current or excessive peak voltage from being added to the base of the switch tube when the power is turned on, resulting in damage to the switch tube.
The name and meaning of capacitors in different circuits
26. Starting capacitor: connected in series with the auxiliary winding of the single-phase motor to provide the starting phase-shifted AC voltage for the motor. After the motor runs normally, it is disconnected from the auxiliary winding.
27. Running capacitor: It is connected in series with the auxiliary winding of the single-phase motor to provide phase-shifted alternating current for the auxiliary winding of the motor. When the motor is running normally, it is connected in series with the auxiliary winding.
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