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Ferrites and accessories

Posted: 24 Jun 2008 ?? ?Print Version ?Bookmark and Share

Keywords:application note? ferrite? filter? broadband? sensor?

This application note discusses the usage and function of Epcos' ferrites and cores in filter, LAN, EMI and power applications; broadband transformers and inductive sensors.

Gapped cores are always used in high quality circuits. In the case of small air gaps (max. 0.2mm) the air gap can be ground into only one core half. In this case, the half with the ground air gap bears the stamp. The other half is blank. The air gap enables the losses in the small-signal area and the temperature coefficient to be reduced by a factor of ?e/?i in the small-signal area. More important, however, is that close AL value tolerances can be achieved.

For fields of application such as matching transformers in digital telecommunication networks or pulse signal transformers, either cores which form a closed magnetic circuit (toroids, double E or double-aperture cores) or paired core sets without air gap are used.

LAN is a connection of local computers in most cases inside a building. The transfer rate values between 10Mbit/s and 100Mbit/s. The transmission rates are 10Mbit/s (10 Base T), 100Mbit/s (100 Base T) and 1Gbit/s (Gigabit Ethernet).

To design the signal 1:1 transformer small toroids are typically used. Its functions are impedance matching and network termination. Due to space restriction the core has to be the smallest possible, that still meets the inductance requirement under the given working conditions (100kHz).

With the ever-increasing use of electrical and electronic equipment, it becomes increasingly important to be able to ensure that all facilities will operate simultaneously in the context of EMC without interfering with each others' respective functions. The EMC legislation which came into force at the beginning of 1996 applies to all electrical and electronic products marketed in the EU, both new and existing ones. So the latter may have to be modified so that they are neither susceptible to EMI, nor emit spurious radiation. Ferrite cores are ideally suited for this purpose since they are able to suppress interference over a wide frequency range.

View the PDF document for more information.

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