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What is the Q value of the inductor?
Sep 22, 2017



What is the Q value of the inductor?


Inductance Q: Also known as the quality factor of the inductor, it is the main parameter for measuring the inductance device. Refers to the ratio of the inductive reactance exhibited by the inductor to its equivalent loss resistance when operating at an AC voltage of a certain frequency. The higher the Q value of the inductor, the smaller the loss and the higher the efficiency.


The quality factor can be written as Q=2pi* energy stored in the circuit/energy consumed in one cycle of the circuit.


The relationship between the passband BW and the resonance frequency w0 and the quality factor Q is: BW=wo/Q, which indicates that the Q is larger, the passband is narrower, and the Q is smaller than the passband bandwidth.


Q=ωL/R=1/ωRC[1] where: Q is the quality factor w is the power supply frequency at the time of circuit resonance L is the inductance


R is the resistance of the string C is the capacitance Q value is the quality factor, it is the ratio of useful work to total work


The quality factor of the inductor is related to the DC resistance of the coil wire, the dielectric loss of the coil bobbin, and the loss caused by the core, the shield, and the like.


The quality factor of the component, ie the magnitude of the Q, depends on the fabrication process, fabrication materials, and application environment of the component. For example, for the same inductor, if the other parameters are unchanged, only the thickness of the wound inductor wire is changed, and the inductance Q of the wire is higher than the Q of the wire. If silver is plated on the wire, the inductance of the silver-plated wire is higher than the inductance of the non-silvered wire. As for the dielectric resonator, its Q value is more dependent on the dielectric resonator material and fabrication process.


The size of the Q value is also related to the operating frequency. The general inductance will increase as the frequency increases. But it has a limit. When the limit frequency is exceeded, the Q value of the inductor drops sharply, and the inductor loses its inductance. At this point, the dielectric resonator, the surface acoustic wave resonator, and the crystal resonator are more conspicuous. When the operating frequency deviates from their resonant frequency, their Q values will drop sharply and they will not work.


The quality factor describes the ratio of the energy stored in the loop to its energy consumption per week.


Because the product of the same frequency band and the quality factor is the resonant frequency of the loop. Therefore, the quality factor and the width of the passband are contradictory in the case of ensuring the resonance point. So can't say that the higher the quality factor, the better, but also the requirements for the frequency band.


The larger the Q value, the narrower the passband of the resonance, that is, the narrower frequency range included. If a wider passband is required, the smaller the Q value, the better.


In the frequency selection circuit (selecting a certain frequency), the blocking circuit (blocking a certain frequency), the absorbing circuit (attenuating a certain frequency), and the notch circuit (removing a certain frequency), a certain frequency f is utilized or removed. At this time, the larger the Q value, the better. This is the frequency f at the resonance of the resonant circuit. When the LC parallel resonant circuit resonates, the circuit impedance is the largest, which is equivalent to an open circuit, so that the frequency signal with the frequency f cannot pass, and this is prevented. The purpose of the signal. When the LC series resonant circuit resonates, the impedance is minimal, and is relatively short-circuited. At this time, the frequency of f is easy to pass, and other signal frequencies are blocked, so that the frequency selection can be achieved.


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