What is Ferrite Bead : Working & Its Uses

The RF systems and converters with high performance and resolution need a less noise power supply design to get the best performance. So filtering of noise in power supply and reduction of cross-talk with high frequency among analog & digital domains is needed particularly on transceivers & mixed-signal converters. An efficient technique that is used for filtering the noise of a high-frequency power supply is called a ferrite bead. It is a passive device used to filter high-frequency noise over a wide frequency range. It turns into resistive on its proposed frequency range & disperses the noise energy in the heat form. The arrangement of this can be done with the power supply in series. It is frequently united with capacitors toward the ground on either side of the bead. So this can form an LPF network and reduces the noise of the high-frequency power supply.


What is Ferrite Bead?

A bead that is made with ferrite material in hollow cylinder-shaped to provide simple as well as economical technique to attenuate or suppress high-frequency ferrite core, noise within electronic circuits is known as ferrite bead. Alternate names of this are ferrite block, ferrite ring, ferrite choke, or EMI filter. Here, ferrite is a semi-magnetic black substance. Ferrites are enclosed in plastic or rubber material to guard & maintain this bead in position. When the power supply line is arranged within the bead then it performs like an RF suppressor.

Ferrite Beads
Ferrite Beads

The impedance range of ferrite bead mainly depends on frequencies because, at less frequency, it has low impedance whereas at high frequencies it has high impedance. Therefore at high frequencies, it has RF interference noise and electromagnetic interference. These bands utilize high-frequency current dissipation within a ferrite ceramic for making high-frequency noise-based suppression devices.


Ferrite Bead Inductance

If we observe the datasheet of any kind of ferrite bead such as ILBB-0603, then we can simply observe three electrical specifications like DC Resistance, Impedance & Rated DC. From the impedance value, we can discover the inductance value for that specific frequency by using the following formula.

XL = 2πfL

Ferrite bead symbol can be represented with an inductor in the circuit that is connected with the resistor in series as shown in the following circuit

Symbol
Symbol

Different Types

Ferrites beads are classified into two types namely chip ferrite beads & wire wound ferrite beads. These beads offer dissimilar reactions to noise reduction. For example, the Wirewound type work over a wide range of frequencies however they offer low resistance within direct current setups. So for properly use them, we need to recognize their electromagnetic characteristics & how they alter throughout use.

Working of Ferrite Bead

Ferrite band is a passive electronic component and the main function of this is to suppress high-frequency signals on a power supply line. The arrangement of this bead can be done in the region of a power line or ground line that is incoming to a specific device like the power cord to a laptop or laptop charger ferrite bead.

Ferrite Bead Design
Ferrite Bead Design

Ferrite beads work on the principle of faraday’s law which states that the magnetic core in the region of a conductor makes a back EMF within the occurrence of a high-frequency signal, fundamentally attenuating the response of ferrite frequency. Typical beads can be obtained from particular makers like Coilcraft because particular projects may need customized beads.

The magnetic material like ferrite is arranged in the region of the power supply that permits an inductive impedance source to pass the signals throughout the line. Practically, a bead is one kind of non-linear component. The frequency characteristics of a ferrite bead will assist you to understand its simplified circuit model. But, these features can modify as a function of temperature & current.

What is the use of Ferrite Bead?

Ferrite bead inductors are mainly used for attenuating the signals which have high-frequency in electronic components because the impedance of ferrite bead is inductive. Once a ferrite choke is arranged over the power supply line and connected to a device, then it detaches high-frequency noise which is occurred on a power connection.

The use of a ferrite clamp is one of several approaches to noise control like that from an SMPS or switched-mode power supply. So, ferrite bead application like a ferrite filter will provide control & removal of conducted EMI.

Between the many applications of these beads like filter, power supply filter bead or an EMI filter bead can be generally rated for a specific DC threshold. Currents higher than the specific value can harm the component. The difficult thing is that this edge is severely affected by heat. When temperature enhances, then rated current will decrease quickly.

The ferrite impedance can be affected by the rated current. When DC enhances, this bead will lose inductance as well as saturate. The impedance of bead can be reduced maximum at comparatively high currents.

How to Select Ferrite Bead?

Selecting a ferrite bead is not difficult, but you want to know how to choose for your design, then the specifications of the bead play a key role. If your circuit board experiences conducted EMI in an exact frequency range & you need to reduce these frequencies, after that this may be the correct choice for your circuit design.

Depending on the inductive performance of these beads, it is normal to close that these beads reduce high frequencies. But, beads do not perform as a wideband LPF because they can simply assist to reduce an exact range of frequencies. You should select a bead range & choke wherever your un-preferred frequencies are within its resistive band.

Before choosing an exact bead for your circuit design, then you have to observe if the designer can give you impedance versus load current arcs for the ferrite bead. If your load currents are extremely high, then you’ll need to choose a bead that can resist them without losing & saturating its impedance in the preferred frequency range.

Ferrite Bead for EMI Suppression

Ferrite bead prevents EMI or electromagnetic interference in two ways from a device otherwise to a device. A conductive cable performs like an antenna if the device generates RF energy that can be broadcasted throughout the cable and performs like an unintentional radiator. So, the bead is necessary for regulatory fulfillment to decrease EMI.

On the other hand, if there are other EMI sources like household appliances, then the bead stops the cable from working as an antenna & obtaining interference from other devices. This is most frequent on data cables as well as on medical devices.

Thus, this is all about an overview of Ferrite Bead. These can be fairly useful, however, if you only understand accurately how they perform. These beads will reduce signals in a quite small band & their efficiency mainly depends on load current & temperature. To use this bead, you should confirm that it reaches your correct specifications. After that, once connecting the ferrite bead, make sure to get voltage drop & heat into account. Here is a question for you, what are the types of ferrite bands?

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