This paper is the first in a six-part series discussing power-supply decoupling and bypass capacitors. Extending a previous four-part series, this series looks at interactions between supply and capacitor, capacitor materials, and simulation models. The focus of this paper is an explanation of the interaction between the power-supply regulator and the decoupling (bypass) capacitor. In addition, the overall impedance seen by the integrated circuit (IC), including capacitors, printed circuit board (PCB) traces, and voltage regulator is assessed.