What is the dropout voltage of a linear voltage regulator?

A linear voltage regulator needs a certain amount of 'headroom' to function properly. This means the raw input voltage must be higher than the stabilized output voltage. The 'dropout voltage' defines this specific required difference. For example, if a 5-volt regulator has a dropout voltage of 2 volts, the input voltage must remain at or above 7 volts to maintain a steady 5-volt output. If the input falls below 7 volts, the required input-to-output difference is no longer met, the regulator 'drops out' of regulation, and the output voltage will begin to sag. Modern electronics often use Low Dropout (LDO) regulators, which are engineered to minimize this required voltage gap, allowing for greater efficiency and longer battery life in portable devices.