A buck converter is disclosed that may operate in a low power mode or a high power mode based on a power requirements of a load. In the high power mode, modifications to increase frequency response include a higher polling frequency for a comparator, a lower impedance divider in a feedback circuit, a higher biasing current for a comparator, and larger switches for providing current to a reactive step-down circuit of the buck converter. In the low power mode these modifications are reversed. The buck converter may make use of an improved strong arm comparator and a circuit for sensing presence of an inductor in the reactive step-down circuit.