What is the meaning of the ESR of the capacitance (I)

ESR is the abbreviation of the three words of EquivalentSeriesResistance. It is translated as "equivalent series resistance".

In theory, a perfect capacitor does not produce any energy loss itself, but in fact, because of the resistance of the material that makes the capacitor, the dielectric of the capacitor is lost, and the capacitor becomes not "perfect" for various reasons. This loss is externally represented as a resistor connected to a capacitor, so a name is called "equivalent series resistance".

The appearance of ESR causes the behavior of capacitor to deviate from the original definition.

For example, we think that the voltage above the capacitor can not be changed. When suddenly an electric current is applied to the capacitor, the capacitor will start to rise from 0 as it charges itself. But with ESR, the resistor itself produces a voltage drop, which causes the voltage at both ends of the capacitor to change abrupt. No doubt, this will reduce the filtering effect of capacitors. Therefore, many high quality power supplies use capacitors with low ESR.

Similarly, in the case of oscillating circuits, ESR will cause serious changes in the function of the circuit, causing circuit failure or even damage.

Therefore, in most cases, the capacitance of low ESR is often better than that of high ESR. But there are exceptions. Sometimes, ESR is also used to do useful things.