The following figure depicts the absolute value of the impedance of the resistor as a function of frequency. As seen, the impedance of the resistor at low frequencies is R. However, when the frequency rises above a certain value, the effect of parasitic capacitance becomes dominant, which causes The resistance impedance decreases. As the frequency continues to rise, the total impedance rises due to the inductance of the leads, and the lead inductance represents an open path or infinite impedance at very high frequencies. As shown in the figure below, the capacitor exhibits the same resonant characteristics as the resistor due to dielectric loss and finite length of leads. Like resistors and capacitors, the high-frequency characteristics of the inductor are also different from the expected characteristics of the ideal inductor, as shown in the following figure: First, when the frequency is close to the resonance point, the impedance of the high-frequency inductor increases rapidly; second, when the frequency continues to increase The influence of the parasitic capacitance C becomes dominant, and the coil impedance is gradually lowered. After the above model analysis, we have actually gone from low frequency systems to high frequency systems. Here is a frequently asked interview question: Supplement: We believe that the rules for high-speed signals are: Rise time "1/6 transmission delay; So what do we think of the rules of "high-frequency signals"? Wavelength / 20 ≤ The set length of the component, or the length of the trace. A 2 cm resistor compared to the wavelength of the signal at various frequencies. (end) Feature: Surgery Goggles,Eye Safety Goggles,Best Safety Goggles,Eye Goggles Protection Guangzhou HangDeng Tech Co. Ltd , http://www.hangdengtech.com
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March 23, 2023