Ceramic capacitor and frequency

The frequency characteristics of the porcelain capacitor refer to the relationship between the capacitance of the capacitor and other parameters as a function of frequency. Generally speaking, when the capacitor is operated at high frequency, as the operating frequency increases, as the dielectric constant of the insulating medium decreases, the capacitance will decrease, the loss will increase, and the distribution parameters of the capacitor will be affected. At high frequency operation, such as the pole piece resistance, the resistance between the lead and the pole piece, the pole piece's own inductance, the lead inductance, etc., will affect the performance of the capacitor. All of this limits the frequency of use of the capacitor. In order to ensure the stability of the ceramic capacitor, the limit operating frequency of the capacitor should generally be chosen to be 1/3 - 1/2 of the natural resonant frequency of the capacitor.

The capacitance and frequency are inseparable, and the relationship should be very close. The high-capacity ceramic capacitors have a large capacitance. The response to high frequencies is poor. The response to low frequencies is good, while the ceramic capacitors with small specifications have low frequency response. Very poor and very good response to high frequencies. But what is the relationship between the size of the high-voltage ceramic capacitor and the frequency? I hope that my colleagues will discuss it together. Capacitance capacity is related to frequency. Before the resonance point, the capacitance decreases with increasing frequency. After the resonance point, the capacitance increases with frequency.

The curve relationship actually refers to the relationship between ceramic capacitance and frequency, that is, the relationship between Z (=ESR+jwL-j/wC) and frequency. In the low frequency range, the capacitance exhibits capacitive reactance characteristics; in the intermediate frequency range, mainly ESR characteristics; in the high frequency range, the inductive reactance dominates.

To put it simply, parasitic inductance and parasitic capacitance are inevitable on the device. As the frequency increases, the reactance of the capacitor will become closer to zero, and the reactance value of the parasitic inductor will gradually increase. Finally, the reactance of the capacitor will exceed the capacitance and the whole device will be inductive. The larger the capacitance, the closer the high-frequency reactance value is to 0, and the easier it is to be surpassed by its own parasitic inductance.