What is a solid-state relay?

A solid-state relay (SSR) is an electronic switching device that turns on or off when a small external voltage is applied across its control terminals. It performs the exact same function as an electromechanical relay but uses entirely solid-state semiconductor components, such as thyristors, TRIACs, or MOSFETs, instead of physical moving contacts and magnetic coils. Because they have no moving parts, solid-state relays offer faster switching speeds, eliminate contact bounce, and are immune to the mechanical wear and tear that plagues traditional relays. Distractors are incorrect because an SSR is not a traditional relay driven by a transistor, nor is it a mechanical latching relay; it completely replaces mechanical components with semiconductor switches.