In a circuit, as long as the wire passes through it, it can be used (I use wires that look like ordinary resistors, and the wires have been threaded and glued, and there are also surface mount forms, but I rarely see them sold). When current passes through a wire, ferrite has almost no impedance to low-frequency currents, while it has a significant attenuation effect on higher frequency currents. The high-frequency current is dissipated in the form of heat, and its equivalent circuit is a series connection of an inductor and a resistor, with the values of both components proportional to the length of the magnetic bead. There are many types of magnetic beads, and manufacturers should provide technical specifications, especially the impedance frequency curve of the magnetic beads.

Some magnetic beads have multiple holes, and using wires to pass through them can increase the impedance of the component (the square of the number of times the magnetic beads pass through). However, the increased noise suppression ability at high frequencies cannot be as much as expected, and using multiple magnetic beads in series would be better.

Ferrite is a magnetic material that undergoes magnetic saturation due to excessive current flow, resulting in a sharp decrease in permeability. Large current filtering should use specially designed magnetic beads in structure, and attention should also be paid to their heat dissipation measures.

Ferrite magnetic beads can not only be used to filter high-frequency noise in power circuits (can be used for DC and AC output), but also can be widely used in other circuits, and their volume can be made very small. Especially in digital circuits, pulse signals contain high-frequency harmonics, which are also the main source of high-frequency radiation in the circuit

Magnetic bead application

Ferrite magnetic beads are also widely used for noise filtering in signal cables. Taking HH-1H3216-500, which is commonly used for power filtering, as an example, the meanings of its model fields are as follows: HH is a series of HH, mainly used for power filtering, and HB series is used for signal lines; 1 indicates that a component encapsulates one magnetic bead, and if it is 4, four are packaged side by side; H represents the constituent substance, H, C, and M represent intermediate frequency applications (50-200MHz), T low-frequency applications (50MHz), and S high-frequency applications (200MHz); 3216 package size, length 3.2mm, width 1.6mm, i.e. 1206 package; 500 impedance (usually at 100MHz), 50ohm. There are three main product parameters: impedance [Z] @ 100MHz (ohm): Typical50, Minimum37; DC Resistance (mohm): Maximum20; Rated Current (mA): 2500