Abstract: Servo data respectively recorded in the peripheral and innermost tracks of a magnetic disk at low and high densities in synchronism with a predetermined write period are read back and binarized by the magnetic head as flux reversal patterns. In this case, on the basis of a table stored in the EEPROM in advance, the filter characteristic of a characteristic variable type low-pass filter is variably set to be a characteristic defined by a low cutoff frequency fc and a small boost amount in the peripheral zone and to be a characteristic defined by a high cutoff frequency and a boost amount, which is large on a high-frequency side, on the central zone. The peak waveforms of a servo signal in the central side are raised to be sharpened, and a qualification level in a pulse decoder is variably set to be high in the outermost tracks and to be low in the innermost tracks.

Abstract: A circuit for detecting contact of a magneto-resistive (MR) head with a disk surface by properly sensing disturbance signals without being effected by noises using a simple configuration. The circuit for detecting contact of the MR head with the disk surface by sensing a disturbance waveform generated by MR head contact with the disk surface comprises a comparator for comparing a signal read out by MR head with a threshold level V.sub.th ; a pulse width limiting circuit for restricting a pulse width x, which is wider than the predetermined pulse width x.sub.1, to a pulse width x.sub.1 ; and a D flip-flop circuit in which an output signal of the comparator being applied to both D terminal and R terminal, and an output signal from the pulse width limiting circuit being applied to T terminal, and an output signal being obtained from an inverted output terminal QC.

Abstract: The magnetic recording apparatus according to the present invention comprises a recording medium in which servo information items are provided on tracks at a predetermined interval, a head for scanning the tracks of the recording medium, a read/write circuit for reading/writing data with respect to each of recording units on the recording medium through the head, a servo circuit for sequentially reading the servo information items through the head, a first control section for performing control on the basis of the servo information items read out by the servo circuit such that drive power is supplied to the read/write circuit, a predetermined time period before a time point when the read/write circuit starts reading/writing of data with respect to a target recording unit, and a second control section for preventing supply of the drive power to the read/write circuit, upon completion of the reading/writing of the data by the read/write circuit.

Abstract: A resonant frequency control circuit communicates with a head of a disk drive and the preamplifier of a read channel. The resonant frequency control circuit is useful in achieving peaking of a readback signal generated by reading data from a magnetic disk. The read channel also includes an equalizer circuit for enhancing equalization of the readback signal. A controller communicates with the read channel and the resonant frequency control circuit for, in one embodiment, selectively adding capacitance to that capacitance which is present in the read element of the head and the preamplifier. By controlling the resonant frequency, this desired signal peaking can be achieved, which is related to the frequencies of the coded data on the disk.

Abstract: A recording and reproducing apparatus of the present invention has a magnetic head used for both recording and reproduction. To perform the changeover between recording and reproduction in a short period of time, a first recording amplifier for supplying a recording signal is provided at one end of the magnetic head, a second recording amplifier for supplying a recording signal of a phase opposite to that of the recording signal supplied to the one end of the magnetic head is provided at the other end of the magnetic head, and a reproduction input amplifier connected to the both ends of the magnetic head is provided. The same bias voltages are supplied through first and second resistors connected to the both ends of the magnetic head.

Abstract: A high input impedance circuit includes an amplifier such as an operational amplifier comprising transistors of a first polarity which serve as a differential pair and input of the amplifier, base of one transistor being caused to serve as a positive input terminal, base of the other transistor being caused to serve as a negative input terminal. The high input impedance circuit further includes a transistor having base connected to the positive input terminal, and a second polarity opposite to the first polarity, wherein collector of the transistor of the second polarity is connected through d.c. path to a first power supply, e.g., ground, and emitter of the transistor of the second polarity is connected through d.c. path to a second power supply, e.g., power supply voltage terminal through a resistor to apply a signal in phase with an input signal delivered to the positive input terminal to the emitter of the transistor of second polarity to thereby allow input impedance to be higher.

Abstract: After an audio signal at a given level is recorded, the recording level is changed and a video signal is recorded. The audio and video signals are reproduced. A first recording level at which the reproduced video signal becomes the maximum level, a second recording level which is smaller than the first recording level and at which the reproduced video signal level becomes the maximum value.times.0.9, a third recording level at which the reproduced audio signal level is equal to or greater than a reference value, and a fourth recording level at which the reproduced audio signal level becomes equal to or greater than the minimum value are stored in storages, respectively. The video head recording current value is controlled according to the optimum recording level found by an arithmetic section based on the stored recording levels.

Abstract: An apparatus for the adaptive cancellation of at least a first pole frequency in a magnetoresistive (MR) head device includes a preamplifier coupled to first and second terminals of the MR head. A signal at a pole frequency produced by the preamplifier is cancelled by a zero boost frequency signal generated as a result of a signal across the MR head read by a differential amplifier. The zero boost frequency signal is passed to the read channel coming from the MR head to cancel the pole.

Abstract: Automatic tracking control apparatus and method.

Abstract: A signal reproducing circuit includes: a magneto-resistive effect head having one end thereof coupled to a first power supply line, for reproducing data recorded on a magnetic recording medium in a read operation; a first constant current source coupled between another end of the head and a second power supply line, for supplying the head with a sense current in the read operation; first and second transistors having collectors thereof coupled to the first power supply line, and responsive to voltage signals obtained from both ends of the head; second and third constant current sources coupled between each emitter of the first and second transistors and the second power supply line, for supplying the first and second transistors with a predetermined constant current in the read operation; a capacitor connected between each emitter of the first and second transistors; and a control circuit responsive to a read/write control signal, for controlling respective ON/OFF timings of the first to third constant curren

Abstract: An arrangement for reading out an information signal from a magnetic record carrier. The arrangement includes a read head having a magneto-resistive (MR) element (R.sub.m1) with a first terminal (3) connected to a first point (13) of constant potential, and a second terminal (4); a bias-current generator (2) having an output (5) for supplying a bias-current to the MR element; and an amplifier circuit (1) having a first terminal (6) coupled to the output (5) of the bias-current generator (2), and a second terminal (7) coupled to the second terminal (4) of the magneto-resistive element (R.sub.m1) so as to form a series arrangement of the bias-current generator, the amplifier circuit and the magneto-resistive element. At an output terminal (8), the information signal is available. The amplifier circuit (1) includes a MOS transistor T.sub.1 coupled between the output terminal (8) and the second terminal (7), and a feedback circuit, including a resistor (R.sub.1) and a capacitor (C.sub.

Abstract: A coil (6) forming part of a tuned circuit (8) is wound around a gapped magnetic core (2). As a magnetic stripe (14) is passed under core (2), variations to the amplitude and frequency of the circuit (8) occur dependent upon the magnetic data on the strip (14). Selected data are manipulated to derive several values (32, 36, 38, and 40) for combination via AND-gate (47). Only if the combination value is above a threshold value is an indication given that the stripe (14) is genuine and not an attempted copy.

Abstract: A new method for overlapping block read events in a disk drive having synchronously sampled data detection channels is presented. In particular, the new method is for overlapping read back processing by real-time and digital signal processing of first and second data blocks from a storage medium. The method includes steps of clocking real-time and digital signal processes by a clock synchronized to the first data block while the first data block is passing by a data transducer head, clocking the digital signal processes for the first data block by an asynchronous clock operating at a nominal data clocking rate after the first data block has passed by the data transducer head and before a clock has synchronized to the second data block following the first data block, and clocking real-time signal processes for the second data block and completing clocking of the digital processes for the first data block by a clock synchronized to the second data block passing by the data transducer head.

Abstract: A disc drive system includes a plurality of subsystems. At least one of the subsystems includes a filter which is completely integrated using a synthetic integrated circuit element.

Abstract: A magnetic data recording system includes an electronically trainable neural network in the read channel. The neural network recognizes reproduced patterns of data bits regardless of distortion introduced by the recording and reproduction process. An electronically trainable analog neural network has weights which are set so that the network recognizes a limited number of bit patterns which are stored on a magnetic disk.

Abstract: A differential amplifier includes an input stage for receiving input signals, an output stage for generating output signals, and an attenuating circuit for attenuating the output signals and feeding attenuation signals back to the input stage. The input stage includes a current switch formed by two transistors connected commonly to a current source and each connected to two load amplifiers. The load amplifiers are controlled by the attenuation signal, to substantially reduce the amplification of the two transistors.

Abstract: A magnetic field generation device generates a magnetic field modulated according to an information signal by switching the direction of a current to be supplied to a magnetic field generation coil of a magnetic head, according to the information signal. The device is provided with a magnetic field generation core, the magnetic field generation coil, an acceleration coil and a driving device. The magnetic field generation coil is wound around the magnetic field generation core. The acceleration coil is connected in parallel with the magnetic field generation coil to shorten a current inversion time upon generation of a magnetic field.

Abstract: An arrangement for reading out an information signal from a magnetic record carrier. The arrangement includes a read head having a magneto-resistive element with a first terminal connected to a first point of constant potential, and a second terminal; a bias-current generator having an output for supplying a bias-current to the MR element and an amplifier circuit having a first terminal coupled to the output of the bias-current generator, and a second terminal coupled to the second terminal of the MR so as to form a series arrangement of the bias-current generator, the amplifier circuit and the MR element. At an output terminal of the amplifier circuit, the information signal is available.

Abstract: A recording/reproducing apparatus for a magneto-resistive (MR) head having a playback amplifier, including a capacitor for a dc feedback low-pass filter for dc feedback to an initial-stage transistor, and a differential amplifier (gm amplifier), and a switching device for the gm amplifier and for the initial-stage amplifier operable at the time of recording/playback switching. The timing of the switching device is deviated for shortening the switching time interval. To this end, an output of the initial-stage transistor of a playback amplifier for a MR head is compared to reference voltage Vref by a gm amplifier and the low-pass filter is constituted by transconductance gm of the gm amplifier and the capacitance of the capacitor, with the dc output of the gm amplifier being fed back to the base of the initial-stage amplifier.

Abstract: A quad burst servo demodulator with adjustable slew rate for hard disk drives. The quad burst servo demodulator includes a peak voltage detecting system for detecting the peak voltages of an input signal, a plurality of storage capacitors for holding voltages proportional to the peak voltages observed by the peak voltage detecting system, and a programmable current source for charging (via an adjustable slew rate) the storage capacitors to voltages proportional to the detected peak voltages of the input signal.

Abstract: An innovative circuit for driving the write head. All of the driving transistors are NPN, and are prevented from saturation. This is achieved by shifting and scaling down the differential drive applied to the pull-up transistors, to drive the pull-down transistors with levels such that the pull-down transistors cannot reach saturation. This provides a very simple circuit in which all four of the drive transistors are NPN, and all are kept out of saturation. Moreover, the peak write current applied to the head is precisely limited.

Abstract: A preamplifier circuit arrangement for a magnetic or magneto resistive transducer, such as a record/replay head, in which a cascode preamplifier stage, and a stage providing a floating reference voltage for a following amplifier, are linked by an emitter coupled pair of transistors, one in each stage, such that the d.c. currents in the two stages flow in common through the transducer.

Abstract: A circuit for processing an input pulse signal of which the slew rate is dependent on pulse frequency comprises an amplifier (30; 78) for receiving the input pulse signal and generating an output pulse signal having transitions of which the slew rate is dependent on a bias current supplied to the amplifier, and a circuit (38-66; 82-108) for supplying bias current to the amplifier, the bias current being representative at least substantially of the frequency of occurrence of pulses in the input pulse signal.

Abstract: An automatic image quality adjusting device for use in a video signal recording/reproducing apparatus includes a reproducing an head for reproducing FM signal from a magnetic recording medium, an envelop detecting unit for detecting an envelop of the FM signal, and grade detecting unit for detecting a grade of the envelop in accordance with an amplitude of the envelop. A frequency characteristics changing unit is provided for changing the frequency characteristics of a processing signal processed in stages between the reproducing head and a display unit in accordance with to the detected grade. Thus, the image quality is automatically adjusted by changing the frequency characteristics of processing signals in response to the detected grade of the envelope.

Abstract: A disk storage device includes at least one disk, a head for scanning a principal surface of the disk in a generally radial direction thereof for reproducing a servo control signal in response to a servo pattern that is recorded on the principal surface, a rotary mechanism for moving the head along the principal surface of the disk generally in the radial direction, an amplifier supplied with the servo signal reproduced at the head for amplifying the same with a predetermined gain, a signal processing circuit for extracting first and second positional control signals each having a phase that is offset with respect to the phase of the other positional control signal by 90 degrees, from the servo control signal, a level detection circuit for detecting a head position at which the first and second positional control signals have simultaneously an identical level and further for detecting the level of the first and second positional control signals at the detected head position, a gain control circuit for control

Abstract: An electrical current-switching driver circuit is provided for switching current through an inductive memory write head on a memory storage device. The driver circuit provides means for reducing distortion in the output current waveform and for minimizing occurrences of breakdown in the switching transistors in the circuit. The circuit uses AC coupling circuitry and small DC holding currents to linearize the current transition during switching transients, thereby eliminating discontinuities which would otherwise appear in the head current output waveform, midway through the switching transients.

Abstract: In a recordable media drive, error processing is implemented in an adjustable read channel equalizer in which gain and bandwidth values can be selectively adjusted. In a write/verify procedure, the gain value is reduced, while the bandwidth is increased, thereby stressing the read channel during verification of written sectors in order to force the failure of marginal sectors. In an error recovery procedure, when a sector error is encountered, the gain value of the adjustable equalizer is initially increased and a sequence of read retries of the failed sector is initiated.

Abstract: Automatic RF signal level control apparatus for a VCR which can keep the RF channel signals recorded on or reproduced from a video tape in the same level by compensating for the level difference between the RF channel signals. The apparatus includes a detecting and comparing section for detecting and comparing the RF channel signal levels recorded or reproduced by channel heads, and converters and a switching section for compensating for the level difference between the RF channel signals according to the result of comparing.

Abstract: A signal processing circuit that includes a differential amplifier and an integrator. The differential amplifier receives at a first input a signal to process and at a second input an offset compensation signal provided by the integrator. The integrator includes a differential transconductance amplifier receiving an output voltage of the signal processing circuit at a first input and a reference voltage at a second input; a capacitor having a first terminal connected to the output of the transconductance amplifier and a second terminal connected to a fixed voltage; and a voltage follower receiving the voltage at the first terminal of the capacitor and providing the offset compensation signal.

Abstract: A data storage system for storing and retrieving data signals on magnetic medium includes a magnetic transducer, a controller for issuing instructions, and a pre-amplifier adaptive to data storage parameters. The pre-amplifier includes a read amplifier having an adjustable gain, a write driver having an adjustable current source, and a serial shift register responsive to the instructions to selectively operate the read amplifier and the write driver and to issue control signals to first and second digital-to-analog converters to adjust the gain of the read amplifier and the current source of the write driver. Preferably first and second multiplexers are responsive to the control signals to select one of a plurality of magnetic transducers.

Abstract: An integrated circuit adapted for use in a data path of a disk storage system of a type wherein data is recorded at different rates depending upon the storage track of the data and includes servo bursts of head positioning signals disbursed throughout the data on all of the tracks. The circuit includes a variable cut off low pass filter that is adjusted both for the rate of data being read and for the rate of the servo bursts when being read. An automatic gain control and a pulse detector are similarly dynamically adjusted in characteristics to fit that of the data and servo bursts when each is being read from the disk. An output of the filter provides both read data and head positioning signals. A write data path is also provided as part of the circuit.

Abstract: The invention concerns differential amplifiers for computer disc drives, implemented in Metal Oxide Semiconductor (MOS) technology. The amplifiers are of the controllable-gain type. Gain is controlled by adjusting the channel current which passes through the differential Field-Effect Transistors (FETs) of the amplifier. The channel current can be viewed as having a constant component, to which is added an adjustment component. The adjustment component does not pass through the active loads of the differential amplifier, thereby allowing a larger change in gain to be attained.

Abstract: 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.

Abstract: A preamplifier provides an output signal which follows a varying resistance of a sensor of a condition or parameter. An example sensor is a magneto-resistive head employed in computer mass storage systems to read magnetic signals recorded on a magnetic tape or disk. The preamplifier uses a current-mode amplifier to increase its bandwidth and reduce signal distortion. A current source, used with the preamplifier or some other circuit, includes a low pass filter to reduce the effects of various noise sources.

Abstract: An image signal recording and reproducing system for recording an image signal on a recording medium and for reproducing the image signal recorded on the recording medium is arranged to perform a reproducing action on the recording medium on which a sampled image signal formed by sampling the image signal is recorded to sample a reproduced signal reproduced from the recording medium and, in outputting a sampled reproduced signal, the level of the reproduced signal to be sampled is controlled according to the sampling phase of the reproduced signal. This arrangement enables the system to record the image signal on the recording medium and to reproduce the image signal without deteriorating the image signal.

Abstract: In a magnetic storage system, an error recovery is performed by reading the magnetic medium again with the filter programmed to a higher boost. If the retry still fails, the magnetic medium is read again with the filter programmed to a lower boost. The filter adjustment can be performed in combination with position adjustment of the read head, i.e. displacing the read/write head from the centerline of the track during error recovery to reduce read errors.

Abstract: A rotary scanning-type magnetic recording and reproduction apparatus comprises a plurality of magnetic heads installed on a rotary drum, and being in contact with a magnetic tape running on the peripheral surface of the rotary drum, for recording the information signal onto the magnetic tape and/or reproducing the information signal from the magnetic tape, a plurality of recording circuits connected to the magnetic heads respectively, for processing the information signal to be recorded on the magnetic tape transferred from outside the rotary drum and output it to the magnetic head, a rotary transformer for transferring the information signal sent from outside the rotary drum to the recording circuits, and a control circuit for sequentially selectively bringing the recording circuits into an active state according to the rotational position of the rotary drum, and bringing the recording circuits into an active state only during a period of time when the information signal is detected.

Abstract: A preamplifier configured for connection to a magnetoresistive transducer makes use of a first and second transistor connected in a common emitter differential pair configuration. The differential pair configuration has a pair of input terminals and a pair of output terminals. A first feedback circuit is included for providing feedback to at least one of a pair input terminals based on selected relatively slowly changing voltages between a pair of preamplifier output terminals. In this manner, the first feedback circuit minimizes differential voltages at the preamplifier output terminals. A second feedback circuit is provided for supplying feedback to at least one of the preamplifier input terminals based on relatively low frequency voltage magnitudes at one of the pair of input terminals. In this manner, a selected common mode voltage magnitude is maintained at one of the pair of input terminals.

Abstract: A continuous-time analog signal filter arrangement, for realizing a magnitude frequency characteristic which increases for increasing frequencies over a part of the operating frequency range of the filter arrangement, includes an input terminal (1) for receiving an input signal, an output terminal (9) for supplying an output signal which is a filtered version of the input signal, and a number of N integrator elements (5.1, 5.2, . . . , 5.N) connected in series and being included in a feedback loop, where N.gtoreq.2. For each of the N integrator elements the relation holds that the input signal of an integrator element is a differentiated version of its output.

Abstract: A device for recording an information signal on a magnetic record carrier comprises a recording amplifier (3), a magnetic head (4), and a controller for controlling the write current amplitude in dependence on temperature variations which occur during recording. This is effected by a temperature detector. The magnetic head (4) has a write section (5) for recording an information signal on the magnetic record carrier in a recording mode of the device, and a read section (6) for reading an information signal from the record carrier in a playback mode of the device. The read section (6) is of the magneto-resistive type. The temperature detector is formed by the read section.

Abstract: The present invention is a read amplifier that is configured for interconnection with a magnetic head through head contacts. The read amplifier includes a differential transistor pair that is connected in a common emitter configuration. The bases of the differential transistor pair are connected across the magnetic head. A bias generator provides a bias current to the bases of the differential pair of transistors through first and second input resistors. The bias generator includes a circuit for providing a compensation voltage to the bases of the differential transistor pair that is based on changes in the bias current supplied to the differential transistor pair.

Abstract: A magnetic head circuit for a plurality of magnetic heads includes two emitter follower transistors for receiving magnetic head writing data, two differential transistors connected to the two emitter follower transistors for performing differential operation control thereover, and two resistors connected to collectors of the two differential transistors for supplying a base current to the two emitter follower transistors, and wherein the emitter follower transistors are connected in series with each other to perform differential switch operations over a magnetic head writing current. A magnetic head fly-back voltage has a clamp voltage which varies according to a writing current flowing through a pair of signal terminals. A pair of differential transistors, whose bases are connected to the pair of signal terminals and whose emitters are connected directly to each other, are operated according to a voltage appearing between the pair of signal terminals.

Abstract: The circuit according to the invention comprises a circuit for receiving an input signal, the amplitude of which is proportional to the frequency of input signal; amplifier for providing an amplified output signal; bandwidth tracking located between input circuit and amplifier and defining a low-pass filtering stage and a voltage divider network, bandwidth tracking being controlled by servo in response to the output of amplifier, so that the upper cutoff frequency of low-pass filtering stage varies in a proportionate manner with the frequency of input signal and so that the amplitude of amplified output signal remains substantially constant.

Abstract: A write driver to operate inductive heads for magnetic recording is disclosed. The inductive recording head is coupled between first and second outputs of a first write driver block. The first and second outputs of the first write driver block are coupled to first and second inputs of a second write driver block, respectively. First and second current sources are coupled to third and fourth inputs of the second write driver block, respectively. A first switching block is coupled to the first current source and to the third input of the second write driver block. A second switching block is coupled to the second current source and to the fourth input of the second write driver block. A first input signal is provided to a first input of the first write driver block and to the first switching block. A second input signal is provided to a second input of the first write driver block and to the second switching block.

Abstract: A magnetic disk includes a servo zone for reproducing signals for control therefrom and a data zone for recording and reproducing a data signal, wherein the servo zone and the data zone are alternately and repeatedly provided on each of annular tracks, and at least a header portion of each of the servo zones is constituted by a recognizable data. A magnetic disk recorder for recording a signal on and reproducing a signal from the thus constructed magnetic disk includes a recording amplifier for supplying a signal to a magnetic head to thereby record the signal on the magnetic disk, and a unit for, upon turning off an operation of the recording amplifier, applying to the recording amplifier a current for generating a magnetic field from the magnetic head directed to the same direction as a magnetized direction of a predetermined bit of a header portion of the servo zone.

Abstract: A closed loop resolution enhancement technique for reducing density effects to permit increased digital data storage density on magnetic media and improve data reliability for at a given density, uses a predetermined test pattern written on the medium to determine the ratio of amplitudes of high and low frequency components of the test pattern and adjust a resolution value. After a test pattern read operation is used to adjust the resolution value, the same value is used during normal data recovery operations.

Abstract: A circuit apparatus for driving a magnetic head to generate a magnetic field wherein a driving frequency of the magnetic head is increased and a recording density of an information recording medium is raised. In this circuit apparatus, a bridge circuit is constructed in which a chief coil for generating a magnetic field is arranged between a first connection node disposed between a serially connected first auxiliary coil and first switch element and a second connection node disposed between a serially connected second auxiliary coil and second switch element, and the magnetic field is modulated in accordance with an information signal by on-off control of the first and second switch elements to change the direction of current flowing in the chief coil. Further, third and fourth switch elements are respectively connected in parallel with the first and second switch elements so that a current path of the chief coil is separated from respective current paths of the auxiliary coils.

Abstract: In a sector servo type hard-disk apparatus, in the case where a recording medium is not manufacture-formatted, gain control data is written/read in/from a CSS zone of the recording medium after power is turned on and before the first seek is executed. The write/read of the gain control data in/from the CSS zone is also executed in accordance with a peak level of an output signal from an AGC amplifier.

Abstract: A recording/reproducing circuit according to the present invention comprises a recording amplifier for outputting a recording signal, a differential amplifier including a pair of transistors, a base of one of the transistors being a (+) side input, a base of the other transistor being a (-) side input, emitters of the transistors being connected commonly to a current source, the (+) side input being supplied with the recording signal, an output signal being fedback to the (-) side input, the output signal being sent to a recording head and means for cutting a current of the current source to thereby stop an outputting of the recording signal from the differential amplifier circuit.

Abstract: In a magnetic head driving circuit, switching devices are turned on/off in response to a recording signal, thereby inverting a drive current to be applied from direct current power sources to a magnetic head coil. Switching devices to be switched in connection with on/off of the switching devices are connected in parallel with dummy loads connected to the direct current power sources in series. In response to the switching of the switching devices, the magnetic head coil and the dummy load alternately function as a load of each auxiliary coil. Impedances of the dummy loads are set to be equal to the impedance of the magnetic head coil, thereby making the total load of each of the auxiliary coils fixed at any time. Since a balance can be established between a value of a drive current in one direction and that of a drive current in the opposite direction, it is possible to reduce jitter of a recording mark and enable the drive current to suddenly rise and fall.