If there is no proper design, ferrite beads could exacerbate rather than correct the noise problem in electric system. Read on to learn how to select the ferrite beads and make full use of your system noise components.

What is ferrite beads?
Ferrite beads is a kind of electronic components, can be resolved in a wider frequency range passive circuit of high frequency noise energy. The equipment of the resistivity is higher than the expected frequency range, eliminating the noise in the form of heat.

Simplify the modeling and simulation of ferrite beads
You can put the ferrite beads is modeled as a resistor, inductor and capacitor of simplified circuit. Usually, the ferrite beads are divided into three categories: response inductance, resistance and capacitance. In order to filter the high frequency noise, such as electromagnetic interference (EMI) filter applications, you should be in the region of the resistance of the circuit deployment magnetic beads. The device used as a resistor, blocking high frequency noise and as a heat dissipation.

Dc bias current
In the choose for high power application of ferrite magnetic bead filter, filter bandwidth and components should be considered relative to the impedance characteristics of the dc bias current. Please remember, in power filtering applications by ferrite beads of the load current is not zero at any time. In addition, as the dc bias current is increased from zero, all these parameters will change significantly. Magnetic core material saturated began in the increase of the dc bias current, greatly reduce the inductance of magnetic beads.

LC resonance circuit
System in the design of ferrite beads, you also need to consider the formant. When noise filtering circuit contains decoupling capacitor, can appear the phenomenon. Ignore this effect may produce harmful results, such as deterioration rather than less ripple and noise energy problems in circuit. Resonance peak change usually occurs on the common DC/DC switch frequency.

Resonance damping method
The variety of ways you can significantly reduce the resonance peak in the circuit. One way is to add a series resistance in decoupling capacitor path. While this approach reduces the system resonance, but under the high frequency, it will damage the bypass performance. Or, you can filter in ferrite beads add a small resistor in parallel, but this design reduces device in high frequency attenuation effect.

Often, the most effective resonance damping technology need to be combined with a large capacitor (CDAMP) and a damping resistor in series (RDAMP). In your noise filtering circuit to add these two components can minimize resonance peak, without affecting the bypass performance, including at high frequency.

In a noisy digital or analog component, ferrite beads can provide significant filter and isolation.