Chip Beads

<Chip Beads> or <Chip Bead> is a common or commercial name of one of the electronic component used for suppressing or absorbing Electro-Magnetic Interference (EMI) signals. Wiki describes this component as <Ferrite bead>. The name <Chip Beads> is cute.

The name of <Chip Bead> may have come from the ones shown in the photo below.

 

The black material is Ferrite. The wire transmits signals. 

Or SMT type looks more like a small bead as no lead wires. See below.

 

As ref

 
https://www.tdk.com/en/tech-mag/noise/05 (TDK)

Chip beads, which cleverly take advantage of the characteristics of ferrite, are often used as a simple and effective countermeasure for these noise problems. Chip beads are named after perforated beads used in ornaments like necklaces. This stems from the early days when conductors were actually placed through hollow ferrite material. Later, in response to the demand for miniaturization of electronic components, chip beads—with a structure in which a coil is formed inside the ferrite body using laminar fabrication techniques—came to be used. Though no longer a hollow structure, the original “bead” name was retained.

 

SMT type is a rather simple but a very clever invention.

 Structure of SMT type Chip Bead - Multilayer structure

Internal Electrode (metal like gold)

The following article explains Chip Bead very well. 

:"

Ferrite Beads Demystified

https://www.analog.com/en/resources/analog-dialogue/articles/ferrite-beads-demystified.html

Ferrite Bead Simplified Model and Simulation 

A ferrite bead can be modeled as a simplified circuit consisting of resistors, an inductor, and a capacitor, as shown in Figure 1a. R_DC corresponds to the dc resistance of the bead. C_PAR, L_BEAD, and R_AC are (respectively) the parasitic capacitance, the bead inductance, and the ac resistance (ac core losses) associated with the bead.

Figure 1. (a) Simplified circuit model and (b) Tyco Electronics BMB2A1000LN2 measured ZRX plot.

Ferrite beads are categorized by three response regions: inductive, resistive, and capacitive. These regions can be determined by looking at a ZRX plot (shown in Figure 1b), where Z is the impedance, R is the resistance, and X is the reactance of the bead. To reduce high frequency noise, the bead must be in the resistive region; this is especially desirable for electromagnetic interference (EMI) filtering applications. The component acts like a resistor, which impedes the high frequency noise and dissipates it as heat. The resistive region occurs after the bead crossover frequency (X = R) and up to the point where the bead becomes capacitive. This capacitive point occurs at the frequency where the absolute value of capacitive reactance (–X) is equivalent to R.

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the bead inductance, and the ac resistance (ac core losses) associated with the bead.

can be re-written as

the ferrite coil inductance, and the ac resistance (ac core losses) associated with the ferrite material.

 

The point is that it uses or must use the ac resistive region of the ferrite material. However the

inductive region of the ferrite coil and the capacitve region of C_{PAR do have some functions.}

 

C_{PAR.is Capacitance Parasitic. See below as ref.}

 

 

 

 

 

 

 

But may not be this simple.

_{Typical XL (Coil reactance) curve}

But XL (Coil reactance) drops as the frequency becomes high (why?). 

 The above TDK article explains

https://www.tdk.com/en/tech-mag/noise/05 (TDK)

However, what differentiates a chip bead from an LPF (low-pass filter) is that it has both inductive (coil) and resistive properties. In ranges where the frequency of the noise is relatively low, a chip bead works mainly as an inductor, reflecting and blocking the noise. As the inductive component increases, so will the impedance. However, beyond a certain frequency, the impedance drops sharply and the noise reflection characteristics also diminish rapidly. The frequency at which this occurs is called the self-resonant frequency.

_{And  XC (Capacitor reactance) drops at very high frequencies.}  

 Typical XC (Capacitor reactance)

 

 

 

_{CPAR values are small.}

sptt