Detector based combination regulator

Methods and apparatus provide multiple input voltage regulation in which one regulator is selected for operation based on input power conditions. In one example, a dual input voltage regulator system in a combination smart card selects between contact and contactless (e.g., RF) operation based on which power source provides the highest available voltage level. A single transistor drop architecture provides low drop-out voltage regulation capability without substantially increased transistor size. In some implementations, multiplexed control of the regulators for each of a number independent power source inputs may be arranged to substantially reduce or prevent reverse current flow through regulators connected to inactive power inputs.