feed through capacitor

Feedthrough capacitors are coaxially constructed capacitors via which DC voltage or low- frequency AC voltage is fed into a metallic housing or chassis.

Feedthrough capacitors are capacitors with three terminals, 3- terminal capacitors. They consist of an outer and an inner electrode and are embedded in the metallic wall. The outer electrode is connected to the conductive case, and the supply voltage is fed into the metallic case via the inner electrode, which has contacts to the outside and inside.

Equivalent circuit diagram of a feedthrough capacitor

Feedthrough capacitors are designed to prevent high-frequency interference signals from entering via the supply voltage. Together with the electronic components connected downstream, they form a low-pass filter through which the DC voltage is allowed to pass, while high-frequency interference signals are blocked. In order to improve the low-pass behavior, connecting leads of feedthrough capacitors are often equipped with ferrite beads.

Chassis with built-in feedthrough capacitors, photo: saba.magnetofon.de

Feedthrough capacitors, which can be ceramic or film capacitors, are used in the supply lines of tuners, RF amplifiers, RF generators and other RF circuits.