Technical Articles / Whitepapers

DC Bias Characteristics of Ceramic Capacitors Written By: Simon Cen Abstract: Most electrical engineers are at least familiar with the different ratings of ceramic capacitors, such as C0G and X7R. In many applications, the meaning of these character codes is relatively unimportant as some other factor, like price or size, may be driving component selection. Designers must be wary, however, as choosing the wrong combination of capacitor dielectric and applied voltage can have critical performance implications for the associated circuit. For class two dielectrics, the change in bulk capacitance with DC bias can be substantial. Understanding why this happens and how to choose a proper ceramic capacitor can eliminate this common pitfall.

Low Inductance Capacitors for High-Speed Decoupling Written By: Robert Lu Abstract: Modern integrated circuits (IC’s) consume power at rapidly varying rates due to the density of circuits on-board and the extreme speed at which they can operate. Power supplies are required to respond to these changes in load current while maintaining a constant operating voltage. This task is becoming increasingly difficult as the complexity of power distribution networks grows and printed circuit board (PCB) design requires optimization for parasitic inductance and capacitance. Therefore, any power supply performance slack must be absorbed by the all-too-common decoupling capacitor. As shown in Figure 1, a decoupling capacitor is simply an additional parallel capacitance that provides a stable voltage and source of current when

Variability and Tolerance of Ceramic Capacitors Written By: Robert Lu Abstract: The multi-layer ceramic capacitor (MLCC) is one of the most common capacitor varieties found in electronic design. It offers a wide range of bulk capacitance and voltage tolerance in numerous form factors at relatively low cost. While these devices have become commonplace in the designers’ tool chest, they exhibit some often overlooked peculiarities. Of primary concern is the sensitivity of effective capacitance to several environmental factors, including temperature, applied bias voltage, and age. If these factors are unaccounted for, the risk of product failure becomes very real, especially in manufacturing variability and overall tolerance stack-up.