what is Feedthrough capacitor ？

Introduction to Feedthrough Capacitors

A feedthrough capacitor is a type of three-terminal capacitor designed specifically for high-frequency filtering. Unlike ordinary three-terminal capacitors, the feedthrough capacitor is mounted directly on a metal panel. This unique structure minimizes grounding inductance and virtually eliminates the negative effects of lead inductance, allowing it to achieve near-ideal filtering performance.

Key Features and Working Principle

• Low Inductance Design: Feedthrough capacitors have extremely low self-inductance, which results in a very high self-resonant frequency. This makes them highly effective for suppressing noise at frequencies above 1 GHz.
• Direct Panel Mounting: By mounting directly to a metal chassis or panel, the capacitor provides an ultra-low impedance path to ground, improving electromagnetic interference (EMI) attenuation.
• Metal Isolation Plate: A metal plate separates the input and output terminals, effectively blocking high-frequency coupling and preventing signal leakage.
• Temperature Stability: Feedthrough capacitors use ceramic dielectric materials, which are sensitive to temperature changes. Choosing the right ceramic material is essential, as temperature shifts can affect capacitance and thus the filter’s cut-off characteristics.

Applications of Feedthrough Capacitors

Feedthrough capacitors are widely used in high-reliability environments where EMI suppression is critical:

• Telecommunications Equipment
• Military and Aerospace Systems
• Industrial Control Panels
• Medical Devices
• Power Supplies and Shielded Enclosures

Filter Structures: C-Type and Pi-Type

• C-Type Filter: Contains a single capacitor connected between the line and ground.
• Pi-Type Filter: Consists of two capacitors and one inductor, offering enhanced performance for broadband EMI suppression.

These structures utilize the internal and external electrodes of ceramic capacitors to effectively block unwanted high-frequency signals.

Why Choose Feedthrough Capacitors?

• Exceptional EMI suppression in the GHz range
• High-temperature stability with suitable ceramic materials
• Compact size and easy integration into hermetic or shielded environments
• Reliable performance in mission-critical applications

Conclusion

Feedthrough capacitors are essential components for any system that requires robust EMI filtering and high-frequency noise suppression. Their superior design and material selection make them a preferred solution in demanding industries such as aerospace, defense, and advanced communications.

For more information on our full range of feedthrough EMI filters, explore our Product Catalog.