what is the difference between ferrite bead And coil ?

[ballimo]

Ferrite Bead And Coil

Hello,

did anyone knows the difference between a ferrite bead and a coil? and in which cases we have to use a ferrite bead instead of a coil?

Many thanks,

Ballimo

 

[karesz]

Ferrite Bead And Coil

Hi,
For me is a ferrite bead(as SMD) a wire in ferrit powder "molded" with some "choke" effect.
A ferrite coil is a component, where is wire around a ferrit piece wounded...
Can be used as choke too, but better as inductance.
K.

 

[ballimo]

Re: Ferrite Bead And Coil

Hi,

why in some design they are using Ferrite bead instead of a coil?

Thanks,
Rami

 

[checkmate]

Re: Ferrite Bead And Coil

Understanding Ferrite Bead Inductors
Ferrite beads are much more compact and can be easily mounted on a PCB.
But it cannot dissipate as much power as coils, and has a limit on the inductances that it can provide, therefore are used more for DC filtering operations, specifically EMI/EMC applications.

 

[karesz]

Ferrite Bead And Coil

@ checkmate,
Tnx, its a good description!
In my opinion are ferrite beads not smaller as chip inductors, but their are for other job constructed.
You can find both sort of components from 0402 (maybe smaller too) packaging up to big ones...
I have had in a project for ex. "200 Ohm, 0603 beads" from TDK and there are specifyed for at 4-500mA_as I remember.
1206 inductances are over all to buy, beginning over 20 years ago, up to ca. 100 uH, for relative high current rates_ I remember ca. 50 mA, but as 2uH for ca. 200mA, i.e. from TDK too 6 Panasonic, BCI Components, Siemens...
Todays 0402 components are in uHs for 10th of mAs to select...
K.

 

[FvM]

Re: Ferrite Bead And Coil

There are different types of ferrite beads. You have leaded and SMD beads with wires or metal ribbons threaded trough a
ferrite tube or block, and you have chip beads, multilayer ferrite and conductor metal designs.

As basic difference to inductors or "coils" they have intentionally low Q to avoid self resonances and achieve a wideband filtering.

See below the impedance characteristic of a 600 ohm 0603 chip bead from Fair-Rite. Other vendor's products are basically similar.
The part is rated for 100 mA, but only few manufacturers are showing unvarnished what the current rating actually means.
I appreciate the Fair-Rite databook for showing this point clearly.