C 4.4. The time constant, t The time constant of electrostatic capacitors is defined in section C1.2.2 as the time needed to discharge a loaded capacitor through the insulation resistance (IR) to 1/e (~37%) of the initial voltage. This constant denominated t(tau) is the product of IR and C (capacitance), usually abbreviated RC. As already mentioned, supercapacitors don’t have any dielectric even if the...
C 4.0 SUPERCAPACITORS C 4.1. Introduction and Basic Function Supercapacitors (or ultracapacitors) are the fastest growing capacitor technology on the market offering very high DC capacitance and high energy densities. Sometimes all supercapacitors are mis-called as EDLC (Electric Double Layer Capacitors), but as we will explain shortly, EDLC is large, but only one part of supercapacitor family. Supercapacitors features sit between capacitors and batteries,...
C 3.8 WET TANTALUM ELECTROLYTICS C 3.8.1. Introduction Wet tantalum capacitors have several advantages over solid tantalum, aluminum electrolytic, and ceramic capacitors. As with all other capacitors, these advantages lead to a very specific “sweet spot” or focused area of applications where the wet tantalum capacitor is the best and preferred choice. Wet tantalums require little derating and offer higher voltages (75 V,...
C 3.7. SOLID NIOBIUM and NIOBIUM OXIDE CAPACITORS Niobium is a sister metal to tantalum, and shares many chemical characteristics with it, in addition to a few disadvantages and advantages of its own when used as a capacitor dielectric. Niobium capacitor technology has existed for decades, but its limitation in maximum rated voltage, lower volumetric efficiency, incompatibility with low ESR polymer electrode, limited range...
C 3.6 SOLID SINTERED TANTALUMS with MANGANESE DIOXIDE C 3.6.1 Introduction We start with cross section schematics of typical SMD tantalum chip construction. Explanation of tantalum MnO2 capacitor inner structure (not to scale) Figure C3-46a. Tantalum MnO2 capacitors Tantalum SMD chip capacitor structure; source: Kemet The tantalum metal has a dielectric constant of approximately 27. The price for solid tantalums is relatively high due...
