What Is an EMI Filter?

EMI stands for Electromagnetic Interference. An EMI filter (electromagnetic interference filter) is a passive component designed to suppress unwanted high-frequency noise while allowing desired low-frequency signals to pass through unimpeded.

How Does an EMI Filter Work?

Typically composed of inductors and capacitors, EMI filters function as low-pass filters. They eliminate electromagnetic noise generated by switching power supplies, motors, or external sources, improving the anti-interference capability and system reliability.

• Suppresses high-frequency noise
• Passes low-frequency useful signals
• Improves electromagnetic compatibility (EMC)

Applications of EMI Filters

EMI filters are widely used in many fields, including:

• Electronic measuring instruments
• Control and automation systems
• Data centers and server rooms
• Switching power supplies and inverters
• Medical, aerospace, and industrial equipment

Feedthrough Capacitors in EMI Filtering

The feedthrough capacitor is a special type of three-terminal capacitor known for its excellent high-frequency filtering capabilities. Unlike ordinary capacitors, it is directly mounted on a metal panel, which offers two key advantages:

• Low grounding inductance due to direct panel mounting
• Minimal lead inductance, enabling high self-resonant frequency

Additionally, the input and output terminals are physically separated by a metal plate, reducing high-frequency coupling. These characteristics result in a performance close to an ideal capacitor in filtering applications.

Benefits of Using Feedthrough Capacitors

• High-frequency attenuation (up to GHz range)
• Compact and reliable for harsh environments
• Ideal for aerospace, RF systems, and defense electronics

Looking for reliable EMI filtering solutions for your system? Contact our engineers to find the best filter configuration for your needs.