An LCA^® feedthrough capacitor is not merely a simple, discrete capacitor. Its sophistication lies in its ability to integrate multiple passive components internally, forming a fully functional filter module. By combining capacitors with ferrite beads (acting as high-frequency inductors) in different topological configurations, it can construct classic filter circuits such as C-type, L-type, LC-type, π (Pi)-type, and T-type, catering to diverse electromagnetic interference suppression needs.

        C-type / L-type: Their advantages include simple structure, low cost, small size, and typically low DC voltage drop. A disadvantage is their limited attenuation performance.

        π-type: This type can provide very high insertion loss, making it particularly suitable for situations involving high-impedance sources and high-impedance loads. However, its ability to withstand inrush current is generally poorer, and it typically has a higher DC voltage drop.

        T-type: Similarly offering high insertion loss, but it is more suited for matching conditions with low-impedance sources and low-impedance loads.

        The theoretical attenuation performance of a circuit structure (filter) is directly related to the number of components it contains, generally following the basic rule of “20 dB increase in attenuation per decade.”

        Single-Element Filter: This typically refers to a single capacitor (shunting noise to ground) or a single inductor (series blocking). These filters are simple in structure but have the most gradual attenuation slope, theoretically providing 20 dB of insertion loss per decade. They are commonly used for suppressing specific high-frequency noise or in less demanding applications.

        Two-Element Filter: This primarily refers to the LC-type circuit, consisting of one series inductor and one shunt capacitor to ground (or vice versa, in L or C configuration). The addition of a second element creates a resonance point, significantly enhancing the attenuation characteristic. The theoretical attenuation slope reaches 40 dB per decade. It can more effectively separate the desired signal from noise across a broader frequency band.

        Three-Element Filter: This category mainly includes the π-type (Capacitor-Inductor-Capacitor) and T-type (Inductor-Capacitor-Inductor) circuits. These are higher-order filters, whose theoretical attenuation slope increases further to 60 dB per decade. They can provide extremely steep attenuation and very high insertion loss values.

——2018.1.25