Capacitor in the electronic field of filtering, signal filtering, bypass, signal coupling, resonance, compensation, energy storage, DC isolation and so on. In the power circuit, often use a large capacitor with small capacitor to do filtering, capacitance has the characteristics of pass and pass straight, high frequency resistance and low frequency; The larger the capacitance value, the lower the passing frequency, so the large capacitance mainly filters low-frequency signals, while the small capacitance filters high-frequency signals. In the power circuit with large capacitors and a variety of small capacitors, you can filter out all kinds of clutter signals in the mains, to ensure the clean power input.
Power filter circuit
In digital circuits, some sensitive signals, such as AD sampling signal, in order to make the signal is stable, usually will add a filter capacitor on the output side, also called decoupling capacitor, removed from some crosstalk signals on the PCB and the interference of power supply, the capacitance value generally take 0.1 uf, the capacitance value can be a good filter to remove the following 5 MHZ jamming signal, To ensure the stability of the signal receiver, sometimes 0.1uF cannot stabilize the output, so it is necessary to use an oscilloscope to check the frequency of the interference signal and then select the capacitance value. If there is a large amount of clutter in the signal, a capacitor with a lower capacitance value can be used; if the signal fluctuates too much, a capacitor with a large capacitance value can be used for stability.
Signal filtering circuit
In some delay circuit, capacitor has a great role, such as the start time of single chip microcomputer, is to use a simple resistance capacitor collocation to form a delay circuit, in some control circuits, in order to save cost and space, the simplest way is to use capacitance and resistance to do delay circuit.
Time delay circuit
Method of resistance capacitance in series, when VCC input voltage, will first through the resistance to the capacitance charging (capacitance can be regard as a battery), when the voltage of the capacitance on rushed to the VCC, stop charging, the capacitor voltage on both ends for VCC, their specific charging time can T = RC calculate by formula, the greater the capacitance, the greater the resistance, the charging time longer, As above T=10K*10uF=10000*0.00001=0.1s(need to pay attention to the unit conversion: ω *F=s),