due to the ESL of the capacitor. At this point, the capacitor begins to behave primarily as an inductance. ESR and dissipation factor tan δ The equivalent series resistance (ESR) summarizes all resistive losses of the capacitor. These are the terminal resistances, the contact resistance of the electrode contact, the line resistance of the electrodes, the electrolyte resistance, and the dielectric losses in the dielectric oxide layer. ESR influences the remaining superimposed AC ripple behind smoothing and may influence the circuit functionality. Related to the capacitor ESR is accountable for internal heat generation if a #ripple current flows over the capacitor. This internal heat may influence the reliability of tantalum electrolytic capacitors. Generally, the ESR decreases with increasing frequency and temperature. Discussions of electrolytic capacitors historically sometimes refer to the dissipation factor, tan δ, in the relevant data sheets instead of ESR. The dissipation factor is determined by the tangent of the phase angle between the subtraction of capacitive reactance XC from inductive reactance XL, and the ESR. If the capacitor's inductance ESL is small, the dissipation factor can be approximated as: The dissipation factor tan δ is used for capacitors with very low losses in frequency determining circuits or resonant circuits where the reciprocal value of the dissipation factor is called the quality factor (Q) which represents a resonator's bandwidth. Ripple current A "ripple current" is the RMS value of a superimposed AC current of any frequency upon a DC current. It arises mainly in power supplies (including switched-mode power supplies) after rectifying an AC voltage and flows as charge and discharge current through the decoupling or smoothing capacitor. Ripple currents generate heat inside the capacitor body. This dissipation power loss PL is caused by ESR and is the squared value of the effective (RMS) ripple current IR. This internal generated heat, in addition to the ambient temperature and possibly other external heat sources, leads to a capacitor body temperature having a temperature difference of Δ T against the ambient. This heat has to be distributed as thermal losses Pth over the capacitors surface A and the thermal resistance β to the ambient. The internal generated heat has to be distributed to the ambient by thermal radiation, convection, and thermal conduction. The temperature of the capacitor, which is established on the balance between heat produced and distributed, should not exceed the capacitors maximum specified temperature. The ripple current is