The difference between the performance and applica

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The difference between the performance and use of magnetic beads and inductance

magnetic beads are widely used in high-frequency circuits. Understanding the performance and use of magnetic beads makes the circuit design more concise and convenient

inductors are energy storage elements, while magnetic beads are energy conversion (consumption) devices. Inductors are mostly used in power filter circuits, focusing on suppressing conductive interference; Magnetic beads are mostly used in signal circuits, mainly for EMI. Magnetic beads are used to absorb UHF signals, such as some RF circuits, PLL, oscillation circuits, and UHF memory circuits (DDR, SDRAM, Rambus, etc.) need to add magnetic beads in the power input part, while inductance is an energy storage element, which is used in LC oscillation circuits, medium and low frequency filter circuits, and its application frequency range rarely exceeds 50MHz

1 chip inductor: inductive components and EMI filter components will be widely used in PCB circuits of electronic equipment. These components include chip inductors and chip magnetic beads. The following describes the characteristics of these two devices. 1. The short arm blade is loose: tighten the blade and analyze their general and special applications. The advantages of surface mount components are small package size and can meet the requirements of actual space. In addition to the different impedance value, current carrying capacity and other similar physical characteristics, other performance characteristics of through-hole connectors and surface mount devices are basically the same. When chip inductors are used, they are required to realize the following two basic functions: circuit resonance and choke reactance. Resonance circuit includes resonance generation circuit with multiple transient overvoltage protection measures, oscillation circuit, clock circuit, pulse circuit, waveform generation circuit, etc. The resonant circuit also includes a high-Q bandpass filter circuit. To make the circuit produce resonance, capacitance and inductance must exist in the circuit at the same time. Parasitic capacitance exists at both ends of the inductor, which is caused by the fact that the ferrite body between the two electrodes of the device is equivalent to a capacitive medium. In the resonant circuit, the inductance must have high Q, narrow inductance deviation and stable temperature coefficient to meet the requirements of narrow-band and low frequency temperature drift of the resonant circuit. High Q circuit has sharp resonance peak. Narrow inductance bias ensures that the resonance frequency deviation is as small as possible. The stable temperature coefficient ensures that the resonant frequency has stable temperature variation characteristics. The difference between standard radial lead-out inductors, axial lead-out inductors and chip inductors is only that the packaging is different. The inductance structure includes coils wound on dielectric materials (usually alumina ceramic materials), or hollow coils and coils wound on ferromagnetic materials. In power applications, when used as a choke, the main parameters of inductance are DC resistance (DCR), rated current, and low Q value. When used as a filter, a wide bandwidth characteristic is desired, so the high-Q characteristic of the inductor is not required. Low DCR can ensure the minimum voltage drop. DCR is defined as the DC resistance of components without AC signal

2 chip magnetic beads: the function of the chip magnetic beads is mainly to eliminate the RF noise existing in the transmission line structure (PCB circuit). The RF energy is the AC sine wave component superimposed on the DC transmission level. The DC component is the required useful signal, while the RF RF energy is the useless electromagnetic interference transmission and radiation (EMI) along the line. To eliminate these unwanted signal energy, chip magnetic beads are used to play the role of high-frequency resistors (attenuators), which allow DC signals to pass through, and filter Bayer helps its customers take a long lead in the market competition through product differentiation. Besides AC signals, such forces typically use hammers or pressure to achieve signals. Usually, the high-frequency signal is above 30MHz. However, the low-frequency signal will also be affected by the chip magnetic beads

chip magnetic beads are composed of soft magnetic ferrite materials, forming a monolith structure with high volume resistivity. Eddy current loss is inversely proportional to the resistivity of ferrite materials. Eddy current loss is proportional to the square of signal frequency. Advantages of using chip magnetic beads: u miniaturization and lightweight. It has high impedance in the frequency range of RF noise, eliminating electromagnetic interference in the transmission line. Closed magnetic circuit structure can better eliminate the series winding of signals. Excellent magnetic shielding structure. Reduce the DC resistance to avoid excessive attenuation of useful signals

significant high frequency characteristics and impedance characteristics (better elimination of RF energy). Eliminate parasitic oscillation in high frequency amplifier circuit. It works effectively in the frequency range of several MHz to hundreds of MHz. To correctly select magnetic beads, we must pay attention to the following points: what is the frequency range of unwanted signals. Who is the noise source. How much noise attenuation is required. What are the environmental conditions (temperature, DC voltage, structural strength). What is the impedance of the circuit and load. Whether there is space to place magnetic beads on the PCB. The first three can be judged by observing the impedance frequency curve provided by the manufacturer. In the impedance curve, three curves are very important, namely resistance, inductive reactance and total impedance. The total impedance is described by zr22 π FL () 2+: =fl. Typical impedance curves can be found in the datasheet of magnetic beads

through this curve, select the magnetic bead model that has the maximum impedance in the frequency range where you want to attenuate the noise and the signal attenuation is as small as possible under low frequency and DC. The impedance characteristics of chip magnetic beads will be affected under excessive DC voltage. In addition, if the working temperature rise is too high or the external magnetic field is too large, the impedance of magnetic beads will be adversely affected

reasons for using chip magnetic beads and chip inductors: whether to use chip magnetic beads or chip inductors mainly depends on application. Chip inductors are needed in resonant circuits. When it is necessary to eliminate unwanted EMI noise, the use of chip magnetic beads is the best choice. Applications of chip magnetic beads and chip inductors: chip inductors: radio frequency (RF) and wireless communication, information technology equipment, radar detectors, automotive electronics, cellular, pager, audio equipment, PDAs (personal digital assistant), wireless remote control system, low-voltage power supply module, etc. Chip magnetic beads: filtering between clock generation circuit, analog circuit and digital circuit, internal connectors of i/o input/output (such as serial port, parallel port, keyboard, mouse, long-distance telecommunications, local area), between radio frequency (RF) circuit and logic equipment prone to interference, filtering high-frequency conducted interference in power supply circuit, EMI noise suppression in computers, computers, video recorders (VCRs), TV systems and handheld. (end)

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