Voltage regulators for battery operated systems are provided. In certain implementations, a voltage regulator is operable in a regulating mode and a bypass mode. In the regulating mode, an input voltage greater than a selected value can be regulated so as to yield a desired output voltage. In the bypass mode, an input voltage at or less than the selected value can be regulated so as to yield an output voltage that substantially tracks the input voltage. Such a capability of switching between two modes can provide advantageous features such as reducing the likelihood of damage in a powered circuit due to high input voltage, and extending the operating duration of a power source such as a rechargeable battery. Also disclosed are examples of how the foregoing features can be implemented in different products and methods of operation and fabrication.