Many modern electronic systems rely on one or more batteries for power. The batteries are typically recharged, for example, by connecting the electronic system to a power source (e.g., an alternating current (AC) power outlet) via a power adapter and cable.
A voltage regulator may provide a power supply rail from a battery. A low dropout (LDO) regulator is one type of linear voltage regulator that is popular in battery powered devices. A low dropout voltage regulator is generally designed to provide a stable regulated output voltage rail in situations where the dropout of the voltage regular is less than or equal to a predetermined minimum value. That is, a low dropout voltage regulator supports stable output voltage rail regulation when the difference between the input voltage VIN and a regulated output voltage VOUT is larger than or equal to the predetermined minimum value.
A low dropout regulator may include a power field effect transistor (FET). Power FETs are generally designed to handle significant power levels. In particular, power FETs support a high voltage range, while providing good efficiency. A power FET, therefore, handles a wide range of operating conditions. So, traditionally, power FETs are fabricated using higher voltage rated devices that consume a large area.