ST Series, Common Mode Chokes

A common mode choke is an essential electrical filter that effectively blocks high-frequency noise, which is commonly present on two or more data or power lines. It selectively allows the desired DC or low-frequency signal to pass through while attenuating the unwanted common mode (CM) noise current. CM noise current often originates from various sources, such as unwanted radio signals, unshielded electronics, inverters, and motors. These sources can generate electromagnetic radiation that couples with the data or power lines, resulting in interference problems within electronic and electrical circuits. If left unfiltered, this noise can disrupt or degrade the performance of sensitive electronic devices. The common mode choke works by utilizing a magnetic core, typically made of ferrite material, and winding the affected lines around it. The windings are designed in such a way that they create opposing magnetic fields when the CM noise current flows through them. This opposing magnetic field effectively cancels out the CM noise, preventing it from propagating further along the lines. By blocking the CM noise, the common mode choke helps maintain signal integrity and reduces the potential for interference in electronic circuits. It is particularly effective in applications where noise rejection is critical, such as in communication systems, power supplies, data transmission lines, and audio/video equipment. In summary, a common mode choke serves as an electrical filter that selectively blocks high-frequency common mode noise while allowing the desired signals to pass through. By mitigating interference problems caused by CM noise, these chokes play a crucial role in ensuring reliable and high-performance operation of electronic and electrical circuits.