Frequency Characteristic of Resistor

Resistor have small parasitic inductance(which is regarded to be connected in serial to the resistor in equivalent circuit) and parasitic capacitance(the capacitance between electrodes regarded to be connected in parallel to the resistor in equivalent circuit). Thus, as the frequency increases, parasitic components make the resistors to have reactance components instead of pure resistance. In other words, attention must be paid when using resistors in high frequency region, since its impedance varies with frequency.

The below image shows the frequency characteristics of thick film flat chip resistors in size 0603 (0.06 inch x 0.03 inch). It shows the impedance change of resistor depends on the resistance. When the resistance is low, parasitic inductance becomes dominant in the high frequency range, which increases impedance . On when the resistance is high, the parasitic capacitance becomes dominant in high frequency range, which decreases impedance. When the resistance is extremely low, specifically under milliohm, decrease in parasitic inductance and an increase in resistance of the resistor itself due to the skin effect can occur even at 1 MHz or less.

In addition, leaded type resistors tend to have larger parasitic inductance than chip type resistors. And among the leaded types, wirewound resistors have higher inductance because the resistive wires are wound in the coil form. Use of the smallest possible chip type resistor gives less frequency effect since larger ones tend to have higher stray capacitance and inductance than smaller ones.