Technological innovation
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Technological innovation
HOTLine：0769-2268 1472
In the electronic circuit, the capacitor is used by AC and DC blocking, also used to store and release charge to act as a filter, the smooth output ripple signal. Small-capacity capacitor, typically used in high-frequency circuits, such as radios, transmitters and oscillators. Large-capacity capacitor is often used for filtering and storage charges. And there is a feature, usually more than 1μF capacitors are electrolytic capacitors, and 1μF less capacitance ceramic capacitors, mostly, of course, there are also other, such as monolithic capacitors, polyester capacitors, small capacity mica capacitors. There aluminum electrolytic capacitors, filled with electrolyte, and leads to two electrodes, as a positive (+) and negative (-) terminals, and other capacitors different, polarity in the circuit can not be wrong, while the other capacitors are There is no polarity.
The two electrodes of the capacitor are connected to the power of positive and negative electrode, then, even if the power is turned off, there will still be two pins between residual voltage (after school tutorials, you can use a multimeter observation), we said capacitor storage charge. Establish a voltage between the capacitor plates, savings from energy, a process called charge the capacitor. Both ends of the capacitor charged a certain voltage. Capacitors store electric charge to process circuit release, known as the capacitor discharges.
Electronic circuits, only in the capacitor charging process, current flows through only after the end of the charging process, the capacitor is not by DC, acts as a "DC blocking" role in the circuit. Circuits, capacitors are often used as coupling, bypass, filtering, etc., are using it, "through exchanges, DC blocking" features. So AC Why can it? Let's look at the characteristics of the alternating current through the capacitor. AC alternating back and forth not only the direction, its size also changes according to the law. A capacitor connected to the AC power supply, the capacitor is continuously charged and discharged, the circuit will be consistent with the alternating current flowing through the variation of the charge and discharge currents.
Selection of the capacitor involves many issues. The first is the problem of pressure. Plus the voltage across a capacitor exceeds its rated voltage, the capacitor will be breakdown. General electrolytic capacitor voltage binning of 6.3V, 10V, 16V, 25V, 50V, etc.
The following is a list of some of the capacitance effect:Coupling capacitors: use in capacitive coupling circuits called coupling capacitance, the extensive use of such a capacitor circuit in RC coupled amplifier and other capacitive coupling circuit, blocking flow from the exchange effect.
Filter capacitor: The capacitors in the filter circuit called a filter capacitor, using this power supply filter capacitor circuit and a variety of filter circuit, the filter capacitor certain signal band is removed from the total signal.Decoupling capacitors, used in the decoupling circuit capacitor called decoupling capacitors, the use of such capacitor circuit in a multi-stage amplifier circuit DC voltage supply, the decoupling capacitors to eliminate harmful low-cross-linked between each amplifier.
High frequency vibration absorption capacitance: use in high-frequency vibration absorption circuit capacitors called high-frequency vibration absorption capacitors in the audio negative feedback amplifier, in order to eliminate high-frequency self-excited oscillation may occur, with this capacitor circuit to eliminate high frequency amplifier may arise whistle.
Resonant capacitor: the LC resonant circuit with a capacitor called resonant capacitor, LC parallel and series resonant circuit capacitor circuit that are required.
Bypass capacitors: use in bypass circuit capacitor called bypass capacitor circuit of a band if you need to remove the signal from the signal, you can use a bypass capacitor circuits, remove the signal according to the different frequencies, with full frequency domain (All AC signal) bypass capacitor circuits and high frequency bypass capacitor circuits.
And capacitance: use in capacitors and circuit called in and capacitors. In the high-frequency and intermediate frequency amplifier radio, TV tuner amplifier, using this medium and capacitive circuits to eliminate self-excitation.
Timing capacitor: The capacitor in a timing circuit called the timing capacitor. Use in through capacitor charging, discharging time control circuit timing capacitor circuit, a control time constant of the size of the effect from the capacitor.
Integrating capacitor: The capacitor in the integrator circuit called integrator capacitor. In sync separation level circuit television field scan, using this integral capacitor circuits to be removed from horizontal and vertical composite sync signal and vertical sync signals.
Differential capacitance: use the differential circuit called differential capacitance of the capacitor. In the flip-flop circuit in order to obtain the steeple trigger signal, using this differential capacitance circuits to (mainly rectangular pulse) signal obtained from a variety of spiers pulse trigger signal.
Compensation capacitor: The capacitors in the compensation circuit called compensation capacitor, the deck bass compensation circuit, the use of such low-frequency compensation capacitor circuit, in order to enhance the playback signal from the low-frequency signal, in addition, there are high frequency compensation capacitor circuit.
Bootstrap capacitor: used in the bootstrap circuit capacitor called bootstrap capacitor, commonly OTL power amplifier output stage circuit using this bootstrap capacitor circuit, by way of a small amount of positive feedback to enhance the positive half cycle of the signal amplitude.
Capacitive divider: in divider circuit called a capacitor divider capacitor in speaker speaker crossover circuit using capacitive divider circuit, so that work in the high-frequency tweeter, mid-range speakers in the band, low frequency Work speaker at low frequency.
Electrolytic capacitor polarity discriminationI do not know the polarity of electrolytic capacitors used multimeter to measure the polarity of the power block.
We know that only electrolytic capacitor connected to the positive power positive (power block when the black pen), negative termination power negative (electrical barrier when the red pen), the electrolytic capacitor leakage current was small (leakage resistance large). On the contrary, the electrolytic capacitor leakage current increases (leakage resistance decreases).
When measuring, first assume that a very "+" pole, let the multimeter black pen contact, the other electrode and multimeter red pen contact, note the hands stop scale (resistance big left hands), then capacitor discharge (only two wires touch it), two pen swap, re-measurement. Two measurements, hands last stop position left (major resistance) is that, is that the black pen then the positive electrolytic capacitor.
When measuring the best selection of R * 100 or R * 1K block. Analyzing quality capacitors with a multimeterAnalyzing quality capacitors with a multimeter
Depending on the capacity of electrolytic capacitor size, usually used multimeter R × 10, R × 100, R × 1K block tested judgment. Red, black pen then negative capacitor, respectively (before each test, the capacitor discharge), by the hands of yaw to judge the quality of a capacitor. If the gauge needles swing quickly to the right, left and then slowly back in situ, in general, capacitor is good. If the gauge needles swing after swing no longer be described capacitor has a breakdown. If the gauge needles swing gradually return to a position stop bits, then the capacitor has leakage. If you do not put hands up, indicating that the capacitor electrolyte has dried up push to lose capacity.
Some leakage capacitor, using the above method is not easy to accurately judge the good or bad. When the value of the capacitor voltage is greater than the battery voltage value multimeter, positively charged electrolytic capacitor according to the time the leakage current is small, a large leakage current when reverse charging characteristics, may be R × 10K block, reverse charging the capacitor, observation whether at the hands remain stable (ie, the reverse leakage current is constant), thus determine the capacitor quality, high degree of accuracy. Black pen then the negative electrode of the capacitor, the red pen then the positive electrode of the capacitor, hands quickly swing, then gradually retreat somewhere to stay does not move, then the capacitor is good, all the hands in a position to stay or remain unstable then gradually slowly moved to the right capacitor has leakage, we can not continue to use. And generally remain stable in the hands 50-- within 200K scale range.
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