November 13, 2020
Essentially, both magnetic beads and inductors suppress high-frequency signals and pass low-frequency signals. The difference between the two is due to the difference in material and technology. The magnetic beads use ferrite, and the resistance of ferrite is the same If the frequency is strongly correlated, it can be approximated that the higher the frequency, the greater the resistance (before the inflection point); while inductance, such as winding inductance, the nature of the material is copper coil, and its DCR is very low;
Equivalent circuit model of magnetic beads
Impedance curve of magnetic beads
It can be seen from the impedance curve of the magnetic bead that the impedance Z curve and the resistance R curve are roughly the same, that is to say, we can approximate the magnetic bead as an energy dissipation device whose resistance increases with increasing frequency. All the high-frequency signals are eaten up and become heat dissipation.
Inductance equivalent circuit model
The impedance curve of the inductor
The impedance curve and the reactance curve in the above figure are basically the same. For the inductor, the reactance is the main consideration. The high-frequency signal on the inductor is reflected back and not converted into heat. The main consideration is the phase change and frequency selection. characteristic.
S21 curve of measured series magnetic beads
S21 curve of measured series inductance
It can also be seen from the above two pictures that for the entire high-frequency signal, the magnetic beads are not rejected and eaten all; but for the inductor, different frequencies are treated differently.
In short, for the magnetic beads, the high-frequency energy is eaten; for the inductor, the high-frequency energy is reflected back; remember the two impedance-frequency curves are clear.
Magnetic beads, eat high-frequency signals; inductance, reflect high-frequency signals; magnetism eats away!