Low dropouts (LDO) are highly sensitive linear control circuits used in linear voltage regulators and LED drivers, among others, that produce a stable DC voltage. They operate even at the smallest level differences between input and output voltage, which can be less than 100 mV.
In terms of circuitry, LDO regulators consist of a reference voltage source, a differential amplifier, and a field-effect transistor( FET). The differential amplifier amplifies the voltage difference between the stable reference voltage applied to one input of the differential amplifier and the voltage deviation of the output voltage, which is fed back to the second input of the differential amplifier. The voltage difference amplified in the differential amplifier controls the field-effect transistor that forms the actuator. It is in the main circuit of the controller and is controlled by the output of the differential amplifier. The dropout voltage is the difference between the input and output voltages of the LDO regulator.