Actuator for a wastegate or a variable turbine geometry and use of an actuator for a wastegate or a variable turbine geometry

The actuator (10) has a rotary drive (12) and a threaded structure (18), a plunger (22) that are connected in preset manner. The plunger is connected to folding gate or variable turbine geometry of exhaust gas turbocharger. A threaded structure is provided for converting the rotational movement of the rotary drive into reciprocating movement of plunger so as to actuate folding gate or variable turbine geometry of exhaust gas turbocharger.