An electromagnetic actuator comprising a soft-ferromagnetic yoke, with an at least substantially cylindrical circumferential wall (11; 11a, 11b, 11c) covered at a first end with a base and at a second end with a top, the circumferential wall defining an axis in a direction from said base end to said top, the soft-ferromagnetic yoke comprising in said axial direction a base yoke section, an intermediate yoke section and a top yoke section, the base yoke section forming the base and a first axial section of the circumferential wall, as well as a base protrusion surrounded with space by said first axial section of the circumferential wall, the intermediate yoke section forming a second axial section of the circumferential wall, and the top yoke section forming the top and a third axial section of the circumferential wall, as well as a top protrusion surrounded with space by said third axial section of the circumferential wall,the base yoke section and/or the top yoke section housing an electromagnetic coil in the space between their protrusion (10a1, 10c1) and their axial section (10a2, 10a2) of the circumferential wall, the intermediate yoke section holding at least one permanent magnet fixed with its first magnetic pole facing an inner surface of the cylindrical wall, and with its second magnetic pole facing an inner space in the intermediate yoke section, the permanent magnet exerting an attractive force having negative stiffness on an axially movable core element housed in said inner space, at least one of the base and the top defining an axially extending opening through which protrudes an actuation rod fixed to the axially movable core element, characterized in that the actuator further comprises a first and a second membrane (18, 19) of an at least substantially non-magnetic material, the first membrane being arranged between the base yoke section and the intermediate yoke section and the second membrane being arranged between the intermediate yoke section and the top yoke section, the axially movable core element being flexibly restrained between the first and the second membrane (18, 19), the membranes forming a resilient element (18, 19) having a stiffness with a value that is greater or equal than a magnitude of said negative stiffness. the circumferential wall defining an axis in a direction from said base end to said top, the soft-ferromagnetic yoke comprising in said axial direction a base yoke section, an intermediate yoke section and a top yoke section, the base yoke section forming the base and a first axial section of the circumferential wall, as well as a base protrusion surrounded with space by said first axial section of the circumferential wall, the intermediate yoke section forming a second axial section of the circumferential wall, and the top yoke section forming the top and a third axial section of the circumferential wall, as well as a top protrusion surrounded with space by said third axial section of the circumferential wall,the base yoke section and/or the top yoke section housing an electromagnetic coil in the space between their protrusion (10a1, 10c1) and their axial section (10a2, 10a2) of the circumferential wall, the intermediate yoke section holding at least one permanent magnet fixed with its first magnetic pole facing an inner surface of the cylindrical wall, and with its second magnetic pole facing an inner space in the intermediate yoke section, the permanent magnet exerting an attractive force having negative stiffness on an axially movable core element housed in said inner space, at least one of the base and the top defining an axially extending opening through which protrudes an actuation rod fixed to the axially movable core element, characterized in that the actuator further comprises a first and a second membrane (18, 19) of an at least substantially non-magnetic material, the first membrane being arranged between the base yoke section and the intermediate yoke section and the second membrane being arranged between the intermediate yoke section and the top yoke section, the axially movable core element being flexibly restrained between the first and the second membrane (18, 19), the membranes forming a resilient element (18, 19) having a stiffness with a value that is greater or equal than a magnitude of said negative stiffness.