Abstract: The gate terminal of a FET is supplied with a bias voltage from a gate biasing circuit and a fluctuation in voltage V.sub.CS applied to a constant-current circuit is detected by a voltage-fluctuation detector. A gate-bias controller controls the gate biasing circuit to lower the gate bias voltage in a case where the fluctuation in voltage V.sub.CS has changed in an increasing direction, and to raise the gate bias voltage in a case where the fluctuation in voltage V.sub.CS has changed in the decreasing direction. Further, there are provided a plurality of constant-current sources having respective FETs and biasing circuits for setting a prescribed power-supply voltage characteristic and a prescribed temperature characteristic. A constant-current circuit is constructed by parallel-connecting the FETs in the plurality of constant-current sources through the drains and sources thereof.

Abstract: A rotor impeller assembly for use with an electomagnetic stator unit including a shaft with a magnetic rotor directly mounted on the shaft. An impeller unit is rotationally mounted with respect to the shaft. A clutch between the magnetic rotor and the impeller unit rotationally drives the impeller unit by means of the magnetic rotor. The magnetic rotor is formed as an injection molded magnet. The impeller unit is used within an aquarium filter for drawing water from the aquarium tank into the aquarium filter for filtration and discharge back into the aquarium tank.