Equivalent Series Resistance (ESR)

The equivalent series resistor (ESR) is the internal loss resistance of a capacitor.

Real capacitors have not only a capacitance C, but also parasitic effects. These undesirable parasitic properties are indicated by the equivalent series inductance (ESL) and the equivalent series resistance (ESR).

Especially with switched mode power supplies, high alternating current loads and high capacitive currents occur, which lead to active losses in the ESR and thus to heating of the capacitor.

The lower the ESR, the higher the quality of the capacitor and the effectiveness as a filter.

In electrolytic capacitors, for example, the ESR is influenced by the material, construction and conductivity of the liquid electrolyte (cathode). For electrolytic capacitors, the cathode contact contributes the largest part of the ESR value. Back