The relationship between ceramic capacitance and frequency

The frequency characteristics of ceramic capacitors refer to the relation of capacitors' capacitance and other parameters with the change of frequency. Generally speaking, when the capacitor is operated at high frequency, as the working frequency increases, as the dielectric coefficient of the insulating medium decreases, the capacitance will decrease, and the loss will increase, and the distribution parameters of the capacitor will be affected. The performance of the capacitors is affected by the high frequency operation, such as the resistance of the electrodes, the resistance between the leads and the electrodes, the inductance of the electrodes and the inductance of the leads. All this limits the frequency of capacitor use. In order to guarantee the stability of ceramic capacitors, the limiting operating frequency of capacitors should be chosen as 1/3-1/2 of the natural resonance frequency of capacitors.

The capacitance of high-voltage ceramic capacitors with large capacity is poor in response to high frequency and good in response to low frequency, while the ceramic capacitors with small capacity are poor in response to low frequency and very good in response to high frequency. But what is the relationship between the capacitance and frequency of high-voltage ceramics? I hope everyone on youdao will discuss it together. Capacitance and frequency are curve relations. Before the resonance point, capacitance decreases with the increase of frequency. After the resonance point, capacitance increases with the increase of frequency.

The curve relation actually refers to the relation between ceramic capacitance and frequency, namely Z(=ESR+ jwl-j /wC) and frequency. The capacitance presents the capacitive resistance in the low frequency range. In the intermediate frequency range, mainly ESR characteristics; In the high frequency range, inductive resistance plays a dominant role.

In simple terms, it is inevitable that the device will have a parasitic inductance and a parasitic capacitance. With the increase of frequency, the capacitance's reactance value will be closer and closer to 0, while the parasitic inductance value will gradually increase. Finally, the reactance beyond the capacitance will make the whole device appear to be inductive. The higher the capacitance, the closer its high frequency reactance is to 0, the easier it is to be surpassed by its parasitic inductance.