The final phrases that spring to mind when we think of ferrites are undoubtedly discovery and technical development. The discovery of hard ferrites or magnet material, on the other hand, provided ancient navigators with the "lodestones" they needed to find magnetic north. The features of hard ferrites piqued Oersted's interest, leading to early research into electromagnetic by Faraday, Maxwell, and Hertz. More research led to the commercial production of soft ferrite passive components in the 1930s and 1940s, allowing development with inductors and antennas.

What does ferrite mean?

Today, power applications and our ongoing effort to minimize electromagnetic interference rely on the usage of highly permeable soft ferrites, which are magnetic cores made up of ceramics blended from a variety of metal oxides. Ferrites' operational characteristics are determined by the types and ratios of metal oxides. Most ferrites are made up of a manganese-zinc mix (Mn-Zn) or a nickel-zinc mix (Ni-Zn). Mn-Zn ferrites are limited to frequencies of 1MHz or fewer due to their high permeability and low specific resistance. Noise suppression is made possible by Ni-Zn ferrites, which have a low permeability and a high specific resistance.

An increase in the magnetic field causes a flux density flow and magnetization in soft ferrites. The ferrite reverts to its original state when a magnetic field is applied in the opposite direction. If the magnetic property of a soft ferrite is strong, a slight change in the magnetic field induces a substantial change in flux density.

Permeability is one of the most important features of ferrites utilised for noise reduction. Magnetic flux can pass through ferrite materials with a higher permeability than if it went through the air. As the temperature rises, the permeability of ferrites increases. However, ferrite loses permeability after reaching a maximum level of permeability at specific temperatures. While temperature affects permeability, it remains constant up to a certain frequency. In most cases, high-permeability ferrite materials are the optimum choice for high-frequency circuits.


Ferrite clamps and chokes are non-linear components because their impedance changes when the load current and voltage drop change. For a narrow band of frequencies, the devices' impedance becomes highly resistant. As the ferrite becomes more capacitive than resistive at high frequencies, the impedance decreases. When the frequency is increased beyond a certain point, the capacitive impedance decreases and the impedance becomes resistive.

To minimise radio frequency interference (RFI) in an electrical conductor, soft ferrite chokes and clamps can be used. As a result, ferrite chokes for switched-mode power supplies can reduce interference. Ferrite chokes, also known as beads, act as a low-pass filter in a circuit, reducing high-frequency EMI. A circuit only allows low-frequency signals to travel through it. Unlike a standard low-pass filter, which attenuates frequencies throughout a wide frequency range, ferrite chokes and clamps only attenuate frequencies that fall within the ferrite's resistive band. With a large magnitude of attenuation over a wide frequency range, lower dc resistance, more design flexibility, wirewound ferrite and and higher current ratings chokes allow more design flexibility.

A ferrite clamp is created when two halves of ferrite are wrapped around a conducting wire, such as a power cable, to provide an inductive impedance for signals going through the cable. Faraday's Law states that in the presence of a high frequency signal, a magnetic core placed around a conductor produces a back electromagnetic force (EMF). Because ferrite has a high permeability, it provides less barrier to the flow of magnetic flux in the conductor, allowing it to absorb noise.

Choose the Best Ferrite Choke or Clamp According to their Application

Because the unwanted frequencies must match with a resistive band of the choke or clamp, choosing a ferrite choke or clamp is dependent on the source of the EMI and the range of unwanted frequencies. The rated dc current of the device must match the currents seen in the circuit, in addition to matching the choke or clamp to frequency requirements. When the circuit current exceeds the rated current, saturation occurs, and the choke or clamp becomes 50% less inductive and has a 90% reduction in impedance. The choke or clamp will no longer be able to suppress EMI as a result of these changes.

Due to their resistance, ferrite chokes and clamps can create voltage dips in a circuit. As high frequency energy dissipates, the resistive qualities of ferrite devices may generate unintended heating. Always double-check the maximum DC current and DC resistance ratings in the manufacturer's specs. Any ferrite choke or clamp must have a DC current rating that is greater than twice the rail's required current. To eliminate voltage drop difficulties, design teams can use PCB design tools and design rules to establish the proper placement for chokes.


Impedance vs load current curves that indicate the characteristics of the devices at specific currents are included in the manufacturer's specifications for ferrite chokes or clamps. The impedance vs frequency response of ferrite chokes and clamps is also shown in the manufacturer's specifications. Furthermore, most manufacturers supply similar circuit models for ferrite chokes and clamps that can be used to simulate systems.

Because ferrite chokes are both inductive and capacitive, circuit designs must account for “Q,” which is the inductor's reactance divided by the ac or rf resistance plus any dc resistance present in the choke windings. In power isolation circuits, high-Q chokes can cause undesirable resonance. The analytic tools in PCB design software can be used to calculate the approximate value of ferrite choke inductance and the resonant frequency cutoff.

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Cosmo Ferrites Limited, one of the leading manufacturer and exporter of soft ferrites, was established in 1986 with its state of the art manufacturing facility in the foothills of Himalaya.

We manufacture E core, Toroidal core(toroids), ROD Core, POT Core, Planar Cores and other some more Soft Ferrites.

With our diverse product range, we interact closely with our customers as a Solution supplier, adhering to strict quality requirements and backed up by a well-connected distribution network and a 24 hour customer support service.