SMD ferrite
SMD ferrites , also known as chip bead ferrites (CBF) or ferrites chip bead , are inductive components from the ferrites group for the assembly of printed circuit boards in surface mounting technology . SMD ferrites are constructed using multilayer technology. NiZn is used as the enveloping ferrite material , while the coil in the inner layer is made from pure silver using a printing process.
The equivalent circuit is a parallel connection of a resistor , coil and capacitor (electrical engineering) . In the low-frequency range the component acts like an ohmic resistor with low resistance, while in the high-frequency range the inductive component of the impedance predominates. Ferrites also have a low electrical capacity .
The main function of an SMD ferrite is the filtering of EMC interferences, such as differential-mode interference . Interference signals on the line in high frequency ranges are converted into heat in the ferrites. Due to the low quality (Q), SMD ferrites have a very good filter effect. The component values are given as impedance in ohms , which are measured at a frequency of 100 MHz in a 50 ohm impedance system (source-sink). SMD ferrites are manufactured in designs from 0201 to 3312 for maximum through currents of up to 10 A ( direct current ).
literature
- Trilogy of inductive components. Application manual for EMC filters, switching regulators and HF circuits. 4th, revised and expanded edition. Swiridoff, Künzelsau 2008, ISBN 978-3-89929-151-3 .