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Feed-Through Capacitor
A capacitor used to pass thru a bulk head.
Feed-Thru Capacitors [Filters] are used to suppress radio frequency/electromagnetic interference [RFI]. Normally these components are chassis mount [panel mount] devices that can pass AC or DC signals but have an internal Shunt capacitor to bypass RFI noise. However there are many styles and types.

The links above point to pages in the Dictionary of Capacitor Terms.

Interconnection Styles
There are many circuit styles, in addition to just a shunt capacitor [circuits shown right and below].

Inductor T-Filter, Capacitor Shunt
Feed-Thru Capacitor Schematics
Feed-Thru Capacitor Circuit Diagram

The circuits above show a simple shunt capacitor, two styles of Inductor/Capacitor circuits an LC Pi circuit and an LC 'T' circuit. These represent the most common interconnect diagrams. Along with a different internal schematic, body styles also change.

Body Styles
Three different body styles are shown below, each completely different from each other.

EMI Feed-Thru Filter Diagram
EMI Filter

The EMI Filter shown above doesn't use a mounting bolt, but could still be used as a chassis mount feed-thru filter by using a clamp.

Chassis Mount Feed-Thru Capacitor Drawing
Feed-Thru Capacitor Diagram

Two different mounting styles are shown; above and below.

Pi-Filter Circuit and component outline
LC Pi Filter Schematic

Feed-Thru capacitors, filters that only contain capacitors are also combined with RF Chokes. Refer here for Chassis RFI Shielding Methods

Military Specifications;
MIL-C-11015, M11015, or MIL-PRF-11693/7.
MIL-PRF-15733; Filters and Capacitors, Radio Frequency Interference, General Specification

MIL-PRF-11693; Capacitors, Feed through, Radio-Interference Reduction, DC (Hermetically Sealed in metal Cases), Established and Non-Established Reliability, General Specification

Filter: A selective network of resistors, capacitors, and inductors that offers comparatively little opposition to certain frequencies, while blocking or attenuating other frequencies. In this case, these filters will only use capacitors or a combination of inductors and capacitors.

When smaller feed-through capacitors are used as part of a connector assembly, the connector is called Pin-Filtered. However no pin-filter devices are shown on this page. But the different contacts are shown to the right.
Refer to the dictionary entry on Passive Filters.

Filter Manufacturers

Chassis Mount Multi-Inductor Feed-Thru Capacitor Schematic Diagrams
Multi-Inductor Feed-Thru Capacitor Diagram

Although these schematic look the same, which they are, they differ in which end connects to the out-side of the chassis. In the first case the capacitor is the outside end, in the second case the Inductor end is to the outside of the case.

Feedthrough capacitors have a structure in which the ground electrode surrounds the dielectric and the signal terminal goes through the dielectric. Feedthrough capacitors are used by making a mounting hole in the shielding case and soldering the ground electrode directly to the shielding case (plate). Since this type of capacitor has no residual inductance on the ground terminal side as well as on the signal terminal side, it can provide nearly ideal insertion loss characteristics.

PC motherboard

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