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Do the Ferrite clamps attenuate wanted differential signals like ethernet signals?

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myatham

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Do the Ferrite clamps attenuate wanted differential signals also like ethernet signals? I mean, i wanted to attenuate common mode radition and hence i am planning to use a ferrite bead with high impedance. I bother whether it can effect my differential signal since the working frequency is close the frequency that we wish to supress.
Please suggest us on this..
 

With both wires of a differential signal going through a ferrite core, the magnetic field from the positive cycle of current from one of the wires is balanced by the equal value negative cycle of current from the other wire. Thus there is no net magnetic field (neglecting fringe effects) from the differential signal and the magnetic core has no effect on it.

Common-mode signals, on the other hand, have a net magnetic field since the AC cycle currents all flow in the same direction, so they will be attenuated by the ferrite core. Thus the core attenuates common-mode signals but passes differential signals without significant attenuation.
 

Ferrite bead and ferrite "clamp" are usually naming different things. Please clarify which kind of ferrite filter respectively common mode choke you are planning. A high impedance common mode choke (e.g. with multiple turns) can be expected to have a certain differential mode attenuation.
 

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