A solid-state regulator is used to:

A solid-state regulator is designed to maintain a stable output voltage despite variations in input voltage or load conditions. This regulation is achieved by varying the conduction of the control elements, which could include transistors or other semiconductor devices. By adjusting the amount of current passing through these elements, the regulator can effectively 'control' the output voltage, ensuring it remains at a desired level. This operation is crucial in many electronic devices, where consistent voltage is necessary for proper functionality.

In contrast, while converting AC to DC is a different function typically associated with rectifiers, limiting output current is more characteristic of current-limiting devices, and enhancing signal strength pertains to amplifiers. Each of these other options addresses different aspects of electronic circuit functionality and does not align with the primary purpose of a solid-state voltage regulator.