The role of chip capacitors in the electrical field (I)

SMD capacitors, people who know this industry know that patch capacitors are widely used. At the same time, the chip capacitor is used as a passive component. The functions frequently used in the power circuit are: the functions of bypassing, decoupling, filtering and energy storage. The main functions in the signal circuit are coupling, oscillation/synchronization and time. The role of the constant. Below we will add an explanation to these.

1. Filtering in the power circuit: Filtering is an important part of the role of chip capacitors. It is used in almost all power circuits. Theoretically (that is, assuming the capacitor is a pure capacitor), the larger the capacitance, the smaller the impedance and the higher the frequency of passing. However, in fact, most of the capacitors exceeding 1 uF are electrolytic capacitors, which have a large inductance component, so the impedance will increase after the frequency is high. Sometimes you will see a small capacitor with a larger capacitance and a small capacitor. At this time, the large capacitor passes through the low frequency and the small capacitor passes through the high frequency. The function of the capacitor is to pass the high impedance and low frequency. The larger the capacitance, the easier the low frequency passes, and the higher the capacitance, the easier it is to pass. Specifically used in filtering, large capacitor (1000uF) filter low frequency, small capacitor (20pF) filter high frequency.

Some netizens have compared filter capacitors to "water ponds." Since the voltage across the capacitor does not change, it can be seen that the higher the signal frequency, the greater the attenuation. It can be said that the capacitor is like a pond, and the water quantity will not be changed due to the addition or evaporation of a few drops of water. It converts the change in voltage into a change in current. The higher the frequency, the larger the peak current, which buffers the voltage. Filtering is the process of charging and discharging.

2. The bypass capacitor is an energy storage device that supplies energy to the local device. It equalizes the output of the regulator and reduces the load requirements. Like a small rechargeable battery, the bypass capacitor can be charged and discharged to the device. To minimize impedance, the bypass capacitor should be as close as possible to the power supply and ground pins of the load device. This can well prevent ground potential elevation and noise caused by excessive input values. The ground bounce is the voltage drop at which the ground connection is passed through a large current glitch.