Abstract: Provided is an electric coil including a wire coated with enamel and spirally wound a predetermined number of times, an insulating member, and an installation member made of plastic, wherein the wire is an aluminum wire coated with enamel and a copper wire is connected to both ends of the aluminum wire such that the electric coil used in an electric motor is formed of an aluminum wire to solve the problems of high cost and weight caused by the use of a conventional copper wire and the problems of corrosion and disconnection caused by the use of a conventional aluminum wire.

Abstract: A filter includes an input and an output. First and second filter stages having respective stage inputs and stage outputs are connected in cascade between the input and the output. Each filter stage includes an amplifier having an amplifier input and an amplifier output and an inner feedback loop connecting the amplifier output to the amplifier input. An outer feedback loop connects the stage output of the second filter stage with the stage input of the first filter stage. The first and second filter stages and the outer feedback loop are arranged so that an s-space closed-loop transfer function of the filter includes two zeros and a single pole.