Abstract: A device includes an element (e.g. in the shape of a sleeve) and a core located in an interior volume defined by the element and at least partially surrounded by the element. The element has two portions: one portion overlaps at least a region of the core thereby to form a capacitor, while another portion surrounds the core thereby to form an inductor. The device may further include an additional capacitor formed by another element that is separated from the core but overlaps at least a region of the core when viewed in a direction perpendicular to the core. The two elements substantially surround the core. The core may be used to hold charge in a non-volatile manner, even when no power is supplied to the device.