Fujitsu Corporation

Takumi Kawai

Akihiko Ono

Chikara Tsuchiya

Shinichiro Suga

This invention provides a horizontal MOS transistor capable of improving current drivability and reducing ON resistance by optimizing the gate wiring structure and the disposition structure of source/drain layers. First gate wirings are disposed in the X direction at a pitch Yin the Y direction and second gate wiringsare disposed in the Y direction with two pieces as a pair such that they meander at a pitch Xin the X direction. The meandering of the second gate wiringis formed so as to sandwich the bent portionssubstantially in the center of the pitch Y. A bottle-like shape diffusion layer region in which the wide-width region and narrow-width region are combined is sectioned by adjacent first and second wirings. A contactfor connecting the diffusion layer region to the wiring layeris disposed in the wide-width region and wiring layersare disposed such that two rows run in parallel in the X direction. A diffusion layer region is a different electrode region from diffusion layer regions adjacent on four sides thereby forming a MOS transistor. Consequently, a horizontal MOS transistor excellent in current drivability for each unit region and having a slight ON resistance is constructed.

Horizontal MOS transistor

A magnetoresistive element input circuit includes a first resistor connected between a magnetoresistive (MR) element and a first power source. A first current source is connected between the MR element and a second power source and supplies a DC bias current to the MR element in an active mode. A second resistor is connected between the MR element and the first current source. A capacitor is connected to a node between the second resistor and the first current source and to the first power supply. A differential amplifier is connected to the MR element. A voltage supply circuit is connected to the node and supplies the node with a voltage, when the input circuit is in an inactive mode, which is substantially equal to the voltage supplied to the node when the input circuit is in the active mode.

Magnetoresistive element input circuit

A constant-current driver circuit for on-off controlling an output current at a high speed is provided. The constant-current driver circuit includes a first MOS transistor to which a reference current is provided and a second MOS transistor connected to the first MOS transistor for generating an output current having a predetermined ratio to the reference current. A switch circuit is connected to the second MOS transistor to on-off control the output current in accordance with the input signal. A bias circuit is connected to the gate of the second MOS transistor to provide a bias voltage to the gate of the second MOS transistor so that variation in the gate voltage of the second MOS transistor is suppressed.

Constant current driver circuit

A noise eliminating circuit eliminates thermal asperity noise in a reproduction signal generated by a magnetic read head in a disk drive. The noise eliminating circuit includes a differential amplifier that receives the reproduction signal and a feedback signal and generates an amplified signal. A detection circuit connected to the differential amplifier detects noise in the amplified signal and generates a control signal. The control signal is activated when the noise is detected. A feedback circuit connected to the differential amplifier and the detection circuit cuts off the amplified signal with a first cutoff frequency when the control signal is not active and cuts off the amplified signal with a second cutoff frequency when the control signal is active.

Noise eliminating circuit

A preamplifying circuit to amplify signals detected by a magnetoresistance device for a magnetic head. Two terminals of the magnetoresistance device are connected via a first resistor to a power source line Vcc and via a second resistor to a current input terminal of a constant current source having an output terminal which is connected to a ground line, respectively. A first capacitor is connected between the power source line Vcc and an input terminal of the constant current source. The two terminals of the magnetoresistance device are connected to bases of first and second transistors, respectively, in a differential amplification circuit. With this, because the input impedances at both terminals of the magnetoresistance device are equal, the external noise added to both of the terminals of the magnetoresistance device via parasitic capacitance become inphase. Also, the noise from the constant current source added to the base of the second transistor via the second resistor and the noise from the constant current source added to the base of the first transistor via the first capacitor and the first resistor become in-phase.

Growing community of inventors

Kasugai, Japan

Takumi Kawai