Abstract: A spindle motor comprising a bracket, a shaft member provided on the bracket, a rotor rotatably mounted to the shaft member through a pair of bearings, a rotor magnet mounted to the rotor, a stator disposed in opposite relation to the rotor magnet, and magnetic fluid sealing means respectively disposed outwardly of a pair of the bearings. The shaft member is provided with an air passage extending in the axial direction, and a communication passage for communicating the air passage with a space between a pair of the bearings. A cap member which is improved in its structure is disposed outwardly of one of the paired bearings. An annular projection for positioning the rotor magnet concentrically with respect to the rotor is provided on a magnet mount portion of the rotor.

Abstract: An amplifier circuit (100) for use in a radio frequency system. The circuit is comprised of a first amplifier (22) having a first input (20) receiving a first signal (16) and a first output (24). A first coupler (18) samples the first input (20) of the first amplifier (22) and a second coupler (26) samples the first output (24) of the first amplifier (22). A third coupler (36) then compares an output of the second coupler (28) and an output of the first coupler (34), producing an error signal (38) which is substantially indicative of the difference between the first input (20) and the first output (24). A fourth coupler (44) combines the error signal (38) with a second signal (48) to produce a composite signal (50), the second signal (48) at least partially correlated with the first signal (16) received by the first input (20) of the first amplifier. A second amplifier (52) is responsive to the composite signal (50) and produces a second output (54).