Switching type step-down voltage regulators are commonly used as the power source for the IC circuit loads. To ensure that the voltage stability is well maintained, the switching type voltage regulator usually uses LC low-pass filter in the output terminal. However, the inductor size and cost are two of the major concerns in the circuit design of this kind of regulator. This paper presents an active-filter based step-down dc-dc switching voltage regulator that could possibly make the whole circuit on chip. The analytical modeling and simulation results show that the proposed voltage regulator can retain the same performance as the LC-based buck converter as we desired.