Thyristor
A thyristor (, from a combination of Greek language θύρα, meaning "door" or "valve", and transistor) is a solid-state semiconductor device which can be thought of as being a highly robust and switchable diode, allowing the passage of current in one direction but not the other, often under control of a gate electrode, that is used in high-power applications like inverters and radar generators. It usually consists of four layers of alternating P- and N-type materials.