What is Ferrite Beads?

Ferrite Bead is an anti-jamming component that has developed rapidly. It is cheap, easy to use, and has a remarkable effect of filtering out high-frequency noise.

Description

In the circuit just run the wire through it (regular resistor-like, the wire is threaded and glued, and there are surface mount versions). When the current passes through the wire, the ferrite has almost no impedance to the low frequency current, but will have a large attenuation effect on the higher frequency current. The high-frequency current is dissipated as heat in it, and its equivalent circuit is an inductor and a resistor in series, and the value of both components is proportional to the length of the bead. There are many types of magnetic beads, and the manufacturer should provide technical specifications, especially the curve of the impedance of the magnetic beads versus frequency. Some magnetic beads have multiple holes. Passing wires through them can increase the impedance of the component (the square of the number of times passing through the magnetic beads), but the increased noise suppression capability at high frequencies cannot be as much as expected. A few magnetic beads would be better.

Ferrite is a magnetic material, which will cause magnetic saturation due to excessive passing current, and the magnetic permeability will drop sharply. High-current filtering should use magnetic beads specially designed in structure, and pay attention to its heat dissipation measures.

Effect

Ferrite beads can not only be used in power supply circuits to filter out high-frequency noise (which can be used for DC and AC output), but also widely used in other circuits, and their volume can be made very small. Especially in digital circuits, since the pulse signal contains high-frequency harmonics and is also the main source of high-frequency radiation in the circuit, it can play the role of magnetic beads in this occasion, and ferrite beads are also widely used in Noise filtering for signal cables.

Application

Because the use of ferrite beads in the circuit can increase the high frequency loss without introducing DC loss, and it is small in size and easy to install on the lead or wire of the interval, the suppression effect of the noise signal above 1MHz is very obvious, so it can be used It is used for decoupling, filtering and parasitic oscillation suppression of high-frequency circuits. Low-impedance power supply circuits, resonant circuits, class C power amplifiers, and thyristor switch circuits, etc., are very effective for filtering using ferrite beads. Ferrite beads can generally be divided into two types: resistive and inductive, and can be selected according to needs when using. The impedance of a single magnetic bead is generally ten to several hundred ohms. If one attenuation is not enough, multiple magnetic beads can be used in series, but usually the effect will not increase significantly when there are more than three.

Due to the inevitable existence of lead resistance, lead inductance and stray capacitance in any transmission line, a standard pulse signal is prone to overshoot and ringing after passing through a long transmission line. Under the condition of the same rise time of the pulse front, the larger the lead inductance is, the more serious the overshoot and ringing will be. The greater the stray capacitance, the longer the waveform rise time, and the increase of the lead resistance will make the pulse Amplitude decreases. In the actual circuit, the method of series resistance can be used to reduce and suppress the overshoot and ringing.

Ferrite suppression components are also widely used on printed circuit boards, power lines, and data lines. For example, adding ferrite beads to the inlet end of the power line of the printed board can filter out high-frequency interference. Ferrite bead or bead is designed to suppress high frequency interference and spike interference on signal lines and power lines, and it also has the ability to absorb electrostatic discharge pulse interference. The numerical value of the two components is proportional to the length of the magnetic bead, and the length of the magnetic bead has a significant influence on the suppression effect. The longer the length of the magnetic bead, the better the suppression effect.

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