An overview of the
Ferrite magnetic materials, is caused by excessive current and magnetic saturation, permeability decline sharply. Large current filter structure should be adopted on specially designed magnetic beads, also notice its cooling measures. As long as the wire in the circuit through it (ordinary resistance appearance, wire has been through and agglutination, also have SMT) in the form of. When the current through the wire, the little ferrite of low frequency current impedance, and will produce large attenuation of high frequency current. In which high frequency current distribution in the form of heat, the equivalent circuit of an inductor and a resistor in series, the value of the two components are linked to the length of the magnetic beads in proportion. Magnetic bead is a lot of more phyletic, the manufacturer shall provide technical indicators, especially the relationship between impedance and frequency magnetic beads curve. Some have multiple holes, magnetic beads with wires through the components can increase the impedance (the number of times square through the magnetic beads), but the increase in high frequency noise suppression ability could not as expected, and by many several series magnetic beads will be better.
Ferrite beads not only can be used to filter out high frequency noise in the power circuit (can be used in the dc and ac output), also can be widely applied to other circuit, the volume can be very small. Especially in the digital circuit, the pulse signal with high order harmonic frequency is very high, is also a main circuit of high frequency radiation source, so can play the role of magnetic beads in this situation, ferrite beads are widely used in filtering the noise signal cable.
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The unit of ferrite beads is the ohm, rather than a hunter, pay special attention on this point. Because the unit of magnetic beads are according to it at a particular frequency impedance to nominal, the unit of impedance is the ohm. Magnetic beads will generally provide the characteristics of frequency and impedance graph, generally it is a standard with 100 MHZ, such as 600 r @ 100 MHZ, which means at the time of 100 MHZ frequency magnetic bead the impedance of the equivalent of 600 ohms.
