A linear regulator is an electronic device that maintains a constant output voltage despite variations in input voltage or load conditions. It operates by dissipating excess voltage as heat, ensuring that the output remains stable. Linear regulators are commonly used in power supply circuits for devices like computers and mobile phones due to their simplicity and low noise. These regulators come in various types, including low-dropout (LDO) regulators, which can function effectively with a small difference between input and output voltage. While they are efficient for low-power applications, linear regulators are less suitable for high-power scenarios because of their heat generation and lower efficiency compared to switching regulators.