and ESR (Equivalent resistance) Yes capacitance Two parameters of A capacitor will generate various impedances due to its structure Inductive reactance The more important ones are ESR equivalent series resistance and ESL equivalent series inductance Capacitive reactance The foundation of. Capacitors provide capacitance. Why do we need resistance? Therefore, ESR and ESL are also required to be low... low; But low ESR/low ESL are usually advanced series. The ESR is related to the capacity, voltage, frequency and temperature of the capacitor. When the rated voltage is fixed, the larger the capacity, the lower the ESR. Some people are used to connecting several small capacitors together to form a large capacitor to reduce impedance. The theory is resistance parallel connection The resistance decreases. However, if we consider the impedance of the solder joint of the capacitor pin, it is not necessarily a gain. Conversely, when the capacity is fixed, select high WV Rated voltage ESR could also be reduced by; Therefore, high withstand voltage has many benefits. Influence of frequency: ESR is high at low frequency and low at high frequency; Of course, high temperature will also lead to the improvement of ESR. The unit of series equivalent resistance ESR is m Ω, and the advanced series capacitors are usually low ESR and low ESL. If the characteristics of low internal resistance and low leakage current are compared, the low internal resistance is easy to achieve, so the capacitance marked low ESR is very common. ESR is related to the loss angle, ESR=tan δ/(ω× Cs), Cs is the capacitance. Sometimes there is Z in the capacitor specification, which is different from the meaning of ESR, but the calculation of Z is related to ESR, and it is also considered that Capacitive reactance and Inductive reactance , is real internal resistance 。 The ESR unit of capacitance mentioned just now is m Ω, which means large capacitance. If 220 μ F small capacitance, its ESR unit is not m Ω but Ω. Early rolling capacitors often had high ESL, and the larger the capacitance, the larger the ESL. ESL often becomes a part of ESR, and ESL will also cause some circuit faults, such as series resonance. However, compared with the capacity, the proportion of ESL is too small, and the probability of problems is very small. In addition to the progress of capacitor manufacturing process, ESL has been gradually ignored, and ESR has been taken as the main reference factor in addition to the capacity.
By the way, the capacitor also has a quality coefficient Q similar to the inductance, which is inversely proportional to ESR and frequency related, and is seldom used.
ESR （equivalent series resistance） 
