Field Effect Transistor - Understanding the Role of Capacitors in Circuits by Their Names
Capacitors are almost indispensable energy storage components in electronic circuits, with the characteristics of blocking DC, connecting AC, and preventing low frequencies. Widely used in circuits such as coupling, isolation, bypass, filtering, tuning, energy conversion, and automatic control. Familiarity with the names and meanings of capacitors in different circuits helps us understand electronic circuit diagrams.
1. The filtering capacitor is connected between the positive and negative poles of the DC power supply to filter out unwanted AC components in the DC power supply, causing the DC level to slip. Large capacity electrolytic capacitors are commonly used, but other types of small capacity capacitors can also be connected in parallel in the circuit to filter out high-frequency alternating current.
2. Decouple the capacitor and connect it between the positive and negative poles of the amplifier circuit to prevent parasitic oscillations caused by positive feedback formed by the internal resistance of the power supply.
3. In AC and DC signal circuits, bypass capacitors are connected in parallel across resistors or across a common potential from a certain point in the circuit to establish a path for AC signals or pulse signals, avoiding voltage drop attenuation caused by AC signal components passing through resistors.
4. Coupling capacitors are used in AC signal processing circuits to connect signal sources and signal processing circuits, or as inter stage connections between two amplifiers, to block DC and allow AC signals or pulse signals to pass through, so that the DC operating points of the front and rear amplification circuits do not affect each other.
5. The tuning capacitor is connected at both ends of the oscillation coil of the resonant circuit to select the oscillation frequency.
6. The auxiliary capacitor connected in series with the main capacitor of the resonant circuit can be adjusted to reduce the frequency range of the oscillation signal and significantly increase the oscillation frequency at the low frequency end. By appropriately selecting the capacity of the pad capacitor, the low-end frequency curve can be raised to approach the ideal frequency tracking curve.
7. Compensation capacitor is an 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. The neutralizing capacitor is connected in parallel between the base and emitter of the transistor amplifier to form a negative feedback network, in order to suppress self-excited oscillations caused by inter electrode capacitance of the transistor.
9. Frequency stabilizing capacitors play a role in stabilizing the oscillation frequency in oscillation circuits.
10. The timing capacitor is connected in series with resistor R in the RC time constant circuit, jointly determining the length of charge and discharge time of the capacitor.
11. The acceleration capacitor is connected to the oscillator feedback circuit to accelerate the positive feedback process and increase the amplitude of the oscillation signal.
12. Shortening capacitors are capacitors connected in series in UHF high-frequency head circuits to shorten the length of oscillating inductors.
13. Clapper capacitor is a capacitor in series with an inductive oscillation coil in a three-point oscillation circuit, which plays a role in eliminating the influence of transistor junction capacitance on frequency stability.
14. The Sira capacitor is a capacitor connected in parallel with the inductor oscillation coil in a three-point capacitor oscillation circuit, which eliminates the influence of transistor junction capacitance and makes the oscillator easy to oscillate at high frequencies.
15. The stabilizing capacitor is used in the frequency detector to stabilize the amplitude of the output signal.
16. In order to avoid the attenuation and loss of frequency division caused by audio modulation signals during processing, the pre emphasis capacitor is set to enhance the network capacitance of the RC high-frequency component.
17. To restore the original audio signal, it is required to attenuate the high-frequency components and noise that have been pre emphasized in the audio signal by setting the capacitor in the RC network.
18. Phase shifting capacitors are capacitors used to change the phase of AC signals.
19. The feedback capacitor is connected across the input and output terminals of the amplifier, allowing the output signal to be fed back to the capacitor at the input terminal.
20. A voltage reducing and current limiting capacitor is connected in series in an AC circuit, utilizing the capacitance impedance characteristics of the capacitor to limit the current of the AC, thereby forming a voltage divider circuit.
21. Reverse capacitors are used in row scanning output circuits and are connected between the collector and emitter of the row output transistor to generate high-voltage row scanning sawtooth wave reverse pulses, with a voltage resistance generally above 1500V.
22. The correction capacitor is connected in series in the deflection coil circuit to correct the extended linear distortion at the edge of the cathode ray tube.
23. The bootstrap boost capacitor utilizes the charging and discharging energy storage characteristics of the capacitor to increase the potential of a certain point in the circuit, so that the potential at that point reaches twice the voltage value of the power supply terminal.
24. The bright spot elimination capacitor is set in the video discharge circuit to eliminate residual bright spots on the cathode ray tube during shutdown.
25. Soft start capacitors are generally connected to the base of the switching transistor of a switching power supply to prevent excessive surge current or peak voltage from being applied to the base of the switching transistor when the power supply is turned on, which may cause damage to the switching transistor.
26. The starting capacitor is connected in series to the secondary winding of a single-phase motor to provide a starting phase shifted AC voltage for the motor. Disconnect from the secondary winding after the motor is running normally.
27. Connect the operating capacitor in series with the secondary winding of the single-phase motor to provide phase shifted AC current to the secondary winding of the motor. Maintain series connection with the secondary winding during normal operation of the motor.
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