what is magnetic ring inductance?

- Aug 09, 2018-

Inductors, we should all have some idea. I don't know what magnetic ring inductors are you familiar with? What does magnetic ring inductance mean? How is it appropriate to understand the inductance of magnetic rings?


Magnetic beads are designed to suppress high frequency noise and peak interference on signal lines and power lines, and have the ability to absorb electrostatic pulses. Magnetic beads are used to absorb uhf signals, such as some RF circuits, PLL, oscillating circuits, including uhf memory circuits (DDR SDRAM, RAMBUS, etc.), which need to add magnetic beads to the input part of power supply.


The function of magnetic beads is mainly to eliminate RF noise existing in transmission line structure (circuit). RF energy is the ac sine wave component superimposed on the dc transmission level, dc component is the useful signal needed, while RF energy is useless electromagnetic interference transmission and radiation along the line (EMI). To eliminate this unwanted signal energy, the chip magnetic beads act as high frequency resistors (attenuators) that allow dc signals to pass through and filter out ac signals. Usually, the high frequency signal is over 30MHz, however, the low frequency signal will also be affected by the chip magnetic bead.


Magnetic beads have high resistivity and permeability, which are equivalent to series resistance and inductance, but the resistance and inductance vary with frequency. Compared with ordinary inductors, it has better high frequency filtering characteristics and presents resistance at high frequency, so it can maintain high impedance in a wide range of frequencies, thus improving the effect of FM filtering


As a power filter, inductors can be used. The circuit symbol of magnetic bead is inductance, but it can be seen from the model that magnetic bead is used in the circuit function, magnetic bead and inductance are the same principle, but the frequency characteristics are different

Magnetic beads are made up of oxygen magnets and inductors are made up of magnetic cores and coils. Magnetic beads transform ac signals into heat energy. Inductors store ac and slowly release it.

Magnetic beads are a major hindrance to high frequency signals, generally 100 ohm /100mMHZ in the specification, it has a much smaller resistance at low frequencies than inductors.

Ferrite beads (Ferrite Bead) is one of the current application development soon anti-interference components, cheap and easy to use, high frequency noise filtering effect is significant.

In a circuit, you just have to pass the wire through it. (I use wires that look like ordinary resistors. The wires have been passed through and glued together. When the current in the wire passes through, ferrite has little resistance to low frequency current, and it has a large attenuation effect to high frequency current. High frequency current is distributed in the form of heat, and its equivalent circuit is a inductor and a resistor in series. The values of both components are proportional to the length of the magnetic bead. There are many kinds of magnetic beads and manufacturers should provide technical specifications, especially the impedance and frequency curve of magnetic beads.

Some magnetic beads have multiple holes through which a wire can increase the impedance of the component (the square of the number of times the magnetic beads are passed through), but at high frequencies the increased noise-suppressing capacity is unlikely to be as large as expected, and it would be better to string several magnetic beads in series.

saturate the magnetic field due to excessive current, and the magnetic conductivity will decrease sharply. Large current filtering should adopt magnetic beads specially designed in structure and pay attention to their heat dissipation measures.

Ferrite magnetic beads can not only be used to filter high frequency noise in power circuit (they can be used for dc and ac output), but also can be widely used in other circuits. Especially in digital circuits, because the pulse signal contains high frequency harmonic and is the main source of high frequency radiation in the circuit, it can play the role of magnetic beads in this situation.


Ferrite magnetic beads are also widely used in signal cable noise removal.