Provided is a circuit to perform single-ended to differential conversion while providing common-mode voltage control. The oscillator includes a resistance element disposed in parallel to the negative resistance element. In order to provide the shell with the same mechanical stability, despite the reduction in wall thickness, as shells whose wall thickness is not reduced, the wound body of the shell is produced from chemical fibers, preferably from synthetic and inorganic chemical fibers. The transfer layer may comprise a thermoplastic resin and a fine particle. The robotic apparatus is able to utilize a tool to perform a task.