What Is a Feedthrough Capacitor?
A feedthrough capacitor is a type of filter element used in electronic circuits. A feedthrough capacitor is a capacitor with a feedthrough connection. A feedthrough connection is a method of cutting the line pattern from which noise is to be removed and inserting a component in between, and it is often used as a noise countermeasure over a wide range of frequencies.
Field-through capacitors are generally three-terminal and are available in leaded and chip types. They are also called feedthrough capacitors or EMI filters.
Uses of Feedthrough Capacitors
Feedthrough capacitors are used as noise-cutoff filters and are often used in electronic equipment’s power supply lines. In recent years, electronic equipment has become increasingly low-voltage and high-frequency due to power saving, and noise countermeasures have become more critical.
Feed-through connections are generally made by connecting feedthrough in series with the power supply line. However, the disadvantage is that current flows directly into the chip, so the device’s rated current is limited.
Principle of Feedthrough Capacitors
One of the most commonly used capacitors is a chip multilayer ceramic capacitor, generally a two-terminal capacitor. The internal structure consists of a thin dielectric sheet sandwiched between layers of electrodes. Although the structure ensures capacitance, a slight inductance component remains inside. Therefore, the residual inductance at higher frequencies becomes non-negligible, resulting in a degradation of high-frequency characteristics.
In contrast, a three-terminal capacitor, such as a feedthrough capacitor, has ground terminals on both sides of the component in addition to the regular capacitor and has a structure that alternately stacks the directly connected electrode and the ground electrode across the dielectric. This structure results in an LC T-type filter configuration, where the ground electrodes are connected over a short distance, thus reducing the effect of the inductance component.
Therefore, compared to general capacitors, the effect of the inductance component is smaller, so the performance does not deteriorate up to the high-frequency range. The component structure is suitable for removing noise up to high frequencies.