Electrical behavior of ceramic chip capacitors is strongly dependent on test conditions, most notably temperature, voltage and frequency. This dependence on test parameters is more evident with Class II ferroelectric …
Frequency characteristics of an ideal capacitor In actual capacitors (Fig. 3), however, there is some resistance (ESR) from loss due to dielectric substances, electrodes or other components in addition to the capacity component C and some parasitic inductance (ESL) due to electrodes, leads and other components.
In the capacitive characteristic region, the larger the capacitance, the lower is the impedance. Moreover, the smaller the capacitance, the higher is the resonance frequency, and the lower is the impedance in the inductive characteristic region. Our explanation of the frequency characteristics of capacitor impedance may be summarized as follows.
This equation indicates that the smaller the electrostatic capacitance and the smaller the ESL of a capacitor, the higher is the resonance frequency. When applying this to the elimination of noise, a capacitor with a smaller capacitance and smaller ESL has a lower impedance at a higher frequency, and so is better for removing high-frequency noise.
1. Frequency characteristics of capacitors The impedance Z of an ideal capacitor (Fig. 1) is shown by formula (1), where ω is the angular frequency and C is the electrostatic capacitance of the capacitor.
When selecting capacitors for use in dealing with noise, one should select the device according to the frequency characteristic of the impedance rather than the capacitance.
Welcome to the Capacitor Fundamentals Series, where we teach you about the ins and outs of chips capacitors – their properties, product classifications, test standards, and use cases – in order to help you make informed decisions about the right capacitors for your specific applications.