Three minutes to understand the Q value and D value of the capacitor

When doing RF, pay special attention to their Q value when choosing the inductor capacitance, what is the Q value? What does the Q value mean, why is it important? Quality factor Q: Character a quality indicator that characterizes an energy storage device (such as inductance coil, capacitance, etc.), and the energy stored in the resonant circuit is the ratio of the peripheral loss energy. The higher the q value of the component is bigger, and the selection of the circuit or the network of the component is better. Or q = reactive power / active power, or ratio of characteristic impedance and circuit resistance. The higher the Q value, the smaller the loss, the higher the efficiency; The higher the Q value, the higher the frequency stability of the resonator, so it can be more accurate. The factor Q is an important parameter representing the quality of the coil. The size of the Q value indicates the size of the inductive line loss, the larger the Q value, the smaller the loss of the coil; it is, the greater the loss. The quality factor Q is defined as: the ratio of the sensing resistance and the coil DC resistance of the coil when the coil is operating at an alternating current voltage of a certain frequency. It can be expressed in formulas as follows: Where: W - Work angle frequency L - coil inductance R - coil total abduction resistance According to the use occasion, the requirements for quality factor Q are also different. For the inductance coil in the tuning circuit, the Q value is high, because the Q value is higher, the smaller the loop is, the higher the efficiency of the loop; the Q value can be low; for low frequencies Or high frequency choke, you can do nothing. In fact, the increase in Q value is often limited by factors, such as the DC resistance of the wire, the dielectric loss of the coil skeleton, the loss caused by core and shield, and the skin effect during high frequency operation. Therefore, the Q value of the coil is impossible to do very high, usually the Q value is several tens of to one hundred, and only four hundred hundred have the highest. The Q value is equivalent to the count of the D value. Loss angle, D value: General electrolytic capacitor because the internal resistance is higher, the D value is higher, its specifications are determined by the capacitance value, which is 0.1-0.24 or less. The plastic film capacitor is low, depending on the material is 0.001- 0.01 or less. The ceramic capacitor is determined by its material, Hi-K Type and S / C Type are 0.025 or less. T / C TYPE has a specification that is higher than 400-1000 in Q value.

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