A Quick Guide To Ferrite Bead Inductor

Electronic circuits ‌make use of ferrite bead inductors for filtering purposes. These inductors are made of ferrite bead, a choke used to minimize or eliminate high-frequency electromagnetic interference and generate a clearer signal in a circuit.

It works similar to a low-pass filter that allows only low-frequency signals to pass through a circuit. When these ferrite beads are equipped in a device, they can enhance its performance by resolving the interference issues significantly.

In this article, we’re going to give a quick brief about ferrite bead inductors so you can leverage them for your power supply needs.

Ferrite Bead Inductor

What is a Ferrite Bead?

A ferrite bead is a device used to suppress unwanted high-frequency signals that can interfere with electrical devices. It helps to attenuate selected frequency bands & becomes resistive.

Usually, it is equipped with capacitors towards the ground on any of the sides of the bead. The bead is a convenient & inexpensive device to use for RF shielding, RF decoupling & noise suppression. It is most effective in transforming the noise energy into heat to disperse it smoothly.

What is a Ferrite Bead Inductor?

A ferrite bead inductor is a passive core made up of a wound coil & two terminals. It is effective for frequencies between a few MHz to GHz & can store energy in a magnetic field. It is composed of a ferrite core that contains a combination of iron oxide & other metals. The installation is very easy with only a single component inserted into the equipment or placed over a wire to filter the signals.

The inductors generate a micro inductance in a low-frequency range. When there are higher frequencies, the resistive component of the inductor releases primary inductance. When they are inserted into a circuit full of noise interference, their resistive impedance prevents the spread of noise signals.

Commonly, ferrite bead inductors are used in analog circuits & signal processing to regulate the flow of current. This is especially required when energy builds up in a magnetic field and current flow needs to be limited.

Advantages of ferrite bead inductor

  • Easy to install
  • Operates at medium & high frequency
  • High value of inductance
  • High magnetic permeability
  • Low eddy current losses
  • Complete screening
  • Excellent dielectric strength

Applications of ferrite bead inductor

Ferrite bead inductors are used in a variety of applications, such as-

  • Chargers & Switch Mode Power Supplies (SMPS)
  • Communication equipment
  • Electronic appliances, like TVs, Laptops, Audio Systems, DVDs, Gaming Systems, etc.

How to Use Ferrite Bead Inductors?

Ferrite bead inductors are commonly used in RF applications. However, there are a few things you need to keep in mind to get the most benefit out of them.

1. Choose the right frequency: Ferrite beads are resistive over one decade of frequency. Hence, it is important to select a ferrite for a specific frequency over which resistive absorption is needed.

2. Handle with care: You need to be very careful while combining ferrite beads with any components that are also reactive in inductive or capacitive regions. Usually, a ferrite bead has a high Q at lower frequencies.

Designing of Ferrite Bead Inductors

The ferrite beads look like toroidal inductors. But they have a greater length to diameter ratio & also a greater outside to inside diameter ratio as compared to ferrite toroids or toroidal cores. Not only this, if the beads are of unique shape & size but the same material, they will still possess different degrees of noise suppression.

Using the beads is unnecessary if capacitors remove unwanted high frequencies effectively. But if it doesn’t happen, you must use the beads to avoid deteriorating the performance of your electronic devices. The beads are sensitive to heat and can handle a limited percentage of DC current. If the limit is exceeded, the beads can be damaged. Hence, you must handle them while taking precautions.

Why should you choose Ferrites for designing inductors?

Ferrites are the perfect material for producing bead inductors. They have a high permeability, which helps to increase the density of the inductors. These inductors behave normally even when kept at lower frequencies.

Not only this, ferrites are highly resistive, which causes the inductors to pass signals up to extremely high frequencies. Then, the inductive reactance affects the circuit and not the resistive eddy current losses.

But when the frequency increases, the losses also increase. Hence, the rise in resistive losses above frequencies between 10 to 100 MHz depends on the ferrite only.

This increase in resistive losses over a specific frequency is the reason ferrite bead inductors are an excellent choice for EMI filtering. This is because the high-frequency signals dissipate in the form of resistive losses (heat) and do not circulate in the system. There is no scope for the signals to radiate.

The self-capacitance of the inductor with high-frequency takes over, which leads to capacitive reactance. Hence, where there are frequencies over 500 MHz, you must stay careful to ensure that the inductor is not capacitive. Otherwise, this will allow the signals to bypass the losses of the inductor.

Ferrite Bead vs Inductors

Ferrite beads are quite similar to an inductor but it doesn’t behave like a typical one. Talking about its structure, the SMD ferrite sleeves consist of an inner coil as an inductor with multiple layers around. No matter what, these two are very different from each other in terms of a range of characteristics given below.

1. Product Specifications

Ferrite bead inductors have different specifications from that other standard inductors. This is because the bead considers the impedance of a specific frequency (ohms unit) band as its specification.

2. Low Q Factor & High R Value

Ferrite beads are components with a low Q factor. It generates heat which makes the entire ferrite hotter to handle, however, the heat is negligible. The losses in these ferrites don’t go with the reactance component but go well with the resistance component.

This implies that ferrite beads absorb more noise than inductors to provide a better noise suppression performance. Hence, ferrites are better than inductors for reducing noise emissions over a wider range of frequencies.

3. DC Current Performance

Inductors can usually sustain higher DC currents while having little impact on the impedance within this range. They also cause no change in the resonance point.

Ferrite beads attain saturation which leads to a decrease in inductance and shifts the resonance point to higher frequencies. Owing to this, ferrite beads look similar to a resistor.

Bottom Line

Ferrite bead inductors are an effective choice for filtering unwanted noise signals. In their resistive region, they absorb signals instead of reflecting them back into the circuit, which may lead to issues later on. Not to forget, they are inexpensive components to use for any circuit. However, you must check the specifications of the ferrite bead as per your needs to ensure you are making the right purchase.

For this, you can reach out to Cosmo Ferrites Limited, a leading manufacturer & supplier of soft ferrites.

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