KR100258976B1 - Pre-amplifier for controlling Magneto-Resistive head for playing back disc of hard disc drive - Google Patents

Abstract

The present invention relates to a preamplifier for controlling a magnetoresistive head for reproducing a disk of a hard disk drive, the preamplifier for controlling a magnetoresistive head for reproducing a disk of a hard disk drive. A first feedback circuit for providing a predetermined voltage bias to the circuit and providing a predetermined voltage bias to return a portion of the voltage bias to zero the DC current output offset error thereby providing a stable voltage bias to the regenerative magnetoresistive head; A second feedback circuit for feedbacking a part of the voltage bias applied to the head to maintain the internal center voltage of the reproducing magnetoresistive head at a ground potential, and a programmable voltage for adjusting the magnitude of the voltage bias provided to the reproducing magnetoresistive head. To the control unit and the reproducing magnetoresistive head By providing the parts of the raw signal amplifier for detecting and amplifying the output has the effect of realizing a low offset.

Description

Pre-amplifier for controlling Magneto-Resistive head for playing back disc of hard disc drive}

The present invention relates to a computer, and more particularly, to a preamplifier for controlling a magnetoresistive head for reproducing a disk of a hard disk drive.

Hard disk drives, which show an increase in data storage density per bit, or data area per bit, of about 30% per year, have been able to achieve higher data storage cost per bit than any other storage system in recent years. It has led to the rapid development of low cost. Advances in media, head technology, and signal processing technologies have accelerated the trend of large-capacity recording data, thanks to the thin and short of hard disk drive systems as the secondary storage devices of today's computers.

A magnetoresistive head is used for reproducing, in order to overcome the confrontation relationship generated by using a thin film head as a reproducing head and a recording head and to improve recording efficiency. It is practical to use a composite head using a thin film head.

The emergence of the magnetoresistive head required a change in the preamplifier that detects the information recorded on the disc, amplifies it without noise, and records the encoded data on the disc. As a result, unlike the thin film head, the lead portion for regeneration is biased to the magnetoresistive head to detect a signal according to a method of detecting voltage bias voltage and voltage bias current sensing. ), Current bias current sensing, and current bias voltage sensing, and single ended / single power depending on the input / output and power supply of the read preamplifier. It is divided into single power method and differential / dual power method. In contrast, the recording portion of the data is almost similar to the conventional thin film amplifier.

In the conventional hard disk drive system, current bias voltage sensing, which is a voltage sensing method that is easy to apply to a magnetoresistive head for reproducing a disk of a hard disk drive having a high performance, and a current biasing method that is easy to implement a circuit. ) Is widely applied. However, the current biasing method has a problem of shortening the life of the head due to the occurrence of electron movement caused by the change, and some hard disk drive system manufacturers require a voltage biasing method. Increasingly, companies are demanding differential / dual power rather than single-ended / single power.

It is an object of the present invention to provide a preamplifier for controlling the magnetoresistive head for reproducing a disk of a hard disk drive in a stable state by making a DC current output offset error zero.

1 illustrates a preamplifier and a peripheral circuit thereof according to the present invention.

FIG. 2 is a detailed circuit diagram of the magneto-resistive head and preamplifier shown in FIG. 1; FIG.

3 is a circuit diagram including a programmable voltage controller in the circuit shown in FIG.

4 is a block diagram showing a configuration of a preamplifier connected to a plurality of magnetoresistive heads.

The present invention for achieving the above object,

A preamplifier for controlling a magnetoresistive head for reproducing a disk of a hard disk drive, comprising: providing a predetermined voltage bias to the reproducing magnetoresistive head and feedbacking a part of the voltage bias to thereby correct a DC current output offset error. A first feedback circuit which is made zero and provides a stable voltage bias to the reproducing magnetoresistive head, and a part of the voltage bias applied to the reproducing magnetoresistive head is fed back to ground the internal center voltage of the reproducing magnetoresistive head to ground potential. A second voltage feedback circuit for maintaining a voltage; a programmable voltage controller for adjusting a magnitude of a voltage bias provided to the reproducing magnetoresistive head; and an amplifier for detecting, amplifying, and outputting a signal generated in the reproducing magnetoresistive head. A hard disk drive, characterized in that It provides a pre-amplifier device for controlling the reproducing magnetoresistive head of the link.

Preferably, a plurality of reproducing magnetoresistive heads are connected to the preamplifier, and when a selection signal is activated, a signal of a corresponding magnetoresistive head is transmitted to the preamplifier.

According to the present invention, the preamplification device realizes a low offset.

Hereinafter, with reference to the accompanying drawings will be described the present invention in more detail.

1 is a diagram illustrating a preamplifier and a peripheral circuit thereof according to the present invention. Referring to Fig. 1, reference numeral 10 denotes a head of a hard disk drive, and reference numeral 12 denotes a head portion having a reproducing magnetoresistive head and a recording thin film head. Reference numeral 14 is a preamplifier that reads a signal from the magnetoresistive head and writes data to the thin film head, and includes a read / write unit 140 and a serial port 142. Reference numeral 16 denotes a read / write channel. The preamplifier 14 amplifies the signal recorded on the disk 10 of the hard disk drive through the reproducing magnetoresistive head and transmits the signal to the read / write channel 16, and also the read / write channel 16. The signal transmitted from the disk is recorded on the disk 10 of the hard disk drive through the thin film head.

FIG. 2 is a detailed circuit diagram of the magnetoresistive head and preamplifier shown in FIG. Referring to FIG. 2, the preamplifier 14 includes a first feedback circuit 21, a second feedback circuit 23, a programmable voltage controller 25, and an amplifier 27. The magnetoresistive head 13 is commonly connected to the first feedback circuit 21 and the second feedback circuit 23.

The first feedback circuit 21 includes NPN transistors Q1 to Q4, resistors R1 to R4, current sources I0 to I3, and operational amplifier gm0. The first feedback circuit 21 provides a predetermined voltage bias to the regenerative magnetoresistive head 13 and returns a part of the voltage bias to zero the DC current output offset error, thereby providing a stable voltage bias for the reproduction. The magnetoresistive head 13 is provided.

The magnetoresistive head 13 is connected to both ends of the emitter of the NPN transistor Q1 and the NPN transistor Q2 and is configured as an equivalent circuit (RLC equivalent circuit) composed of a resistor, a coil, and a capacitor. The current flowing through the current source I1 flows to the current source I0 through the resistor Rh of the magnetoresistive head 13 and to the current source I2 through the resistors R3 and R4. At this time, when the voltage generated in the resistor Rh of the magnetoresistive head 13 and the voltage generated in the resistors R3 and R4 are different, a DC current offset error between the voltage terminals V0 + and V0- ) Will occur. Then, the magnitudes of the signals RDY and RDX output through the amplifier 27 are changed. In order to prevent this, the operational amplifier gm0 feedbacks signals generated at the voltage terminals Vo- and Vo +. That is, the DC current offset error is eliminated due to the operation of the first feedback circuit 21 and the voltage applied to the magnetoresistive head 13 in this stable state (zero field state of the disk) is internal to the magnetoresistive head 13. It is biased as it is to the resistor Rh.

In addition, the capacitor Cex0 connected to the resistors R3 and R4 is composed of an external capacitor, and is used to remove noise coupling due to biasing of the magnetoresistive head 13. The configuration of the common emitter (CE) or common base (CB) of the NPN transistor (Q1) and the NPN transistor (Q3) or the NPN transistor (Q2) and the NPN transistor (Q4) is a preamplifier (mirror effect) In order to prevent the deterioration of the high frequency characteristic of 14), the load resistors R1 and R2 are composed of resistors having low dependence on manufacturing process or external environment change for realizing low offset amplification. The first feedback circuit 21 composed of the voltage terminals V0 + and V0- including the NPN transistor Q1 and the NPN transistor Q2, the operational amplifier gm0 and the capacitor cex1 outputs a DC current in a stable state. It is for zeroing the offset error and has a transfer function as shown in Equation 1 below.

here, May be adjusted by the capacitor cex1 as the dominant pole point of the first feedback circuit 21. Is usually set to 0.1 to 0.3, and there is a trade-off between the set-up time of the preamplifier 14 and the overall preamplifier 14 in the low frequency region. To have. In addition, the current source ( ) Is an element for minimizing the DC current output offset error in the first feedback circuit 21.

The second feedback circuit 23 includes resistors R10 to R12 and R30, a switching means SW1, operational amplifiers gm1 and OPAMP3, an NPN transistor Q13, and a capacitor Cex2. The second feedback circuit 23 feedbacks a part of the voltage bias applied to the regenerative magnetoresistive head 13 to maintain the internal center voltage of the regenerative magnetoresistive head 13 at ground potential GND. Accordingly, even when the disk 10 of the hard disk drive and the magnetoresistive head 13 have the same potential, the magnetoresistance is shortened even if the disk 10 and the magnetoresistive head 13 of the hard disk drive are shorted. The head 13 is prevented from being damaged.

The second feedback circuit 23 is a magnetoresistive head in which an expensive magnetoresistive head 13 flows excessive current through the magnetoresistive head 13 when the expensive magnetoresistive head 13 is shorted with the surrounding environment, in particular, the disk 10 of the hard disk drive. In order to protect the (13) from being damaged, the internal center voltage of the magnetoresistive head 13 is detected through the resistors R10, R11 (> > Rh, R12), and then the ground potential GND In comparison, the output is fed back until the internal center voltage of the magnetoresistive head 13 becomes the ground potential GND so that a ground potential GND almost equal to that of the disk 10 of the hard disk drive can be obtained. do. The output VMF of the operational amplifier OPAMP3 may represent the internal center voltage of the magnetoresistive head 13. The transfer function of the second feedback circuit 23 is expressed by Equation 2 below.

here, Can be controlled by the capacitor Cex2. Therefore, when the magnetoresistive head 12 and the disk 10 of the hard disk drive are shorted for a short period, the dominant polarity is set so that the second feedback circuit 23 does not respond. The switching means SW1 is for selecting each channel in a multi-channel configuration, and operates each channel according to the selection signals Csi, i = 0, 1, 2...

The current source I3 is for minimizing the error of the ground potential GND and the internal center voltage of the magnetoresistive head 13 by the second feedback circuit 23.

The transfer function in the intermediate band of the preamplifier 14 (hundreds [KHZ] to 150 [MHZ]) is a signal detected at both ends of the magnetoresistive head 13 by the input voltage represented by Equation 4 below. It is expressed as Equation 5 below.

here, Represents the resistance of the activated emitter, Denotes the base spreading resistance of the NPN transistor Q1 and the NPN transistor Q2, that is, the data recorded on the disk 10 of the hard disk drive is the resistance of the magnetoresistive head 13 due to the change in magnetic flow. A change (dh) is generated and detected as a minute signal at both ends of the magnetoresistive head 13, and amplified by about 50 dB without noise and output.

The programmable voltage controller 25 adjusts the magnitude of the voltage bias provided to the regenerative magnetoresistive head 13. The programmable voltage control 25 is shown in detail in FIG. The amplifier 27 senses and amplifies a signal generated in the reproduction magnetoresistive head 13 and outputs the signal to the weather / recording channel (16 in FIG. 1).

3 is a circuit diagram of a programmable voltage controller included in the circuit of FIG. 2. Referring to FIG. 3, the programmable voltage controller 25 may include NPN transistors Q6, Q7 and Q11 to Q20, NMOS transistors MN1 and MN2, PMOS transistors MP3 to MP8, and resistors R13 to R18. , R21, R22, and R234, operational amplifiers V-TO_1, a serial port 31, and a bandgap voltage generator 33. According to FIG. 3, the preamplifier 14 is configured to adjust the bias by the serial control input. That is, the serial port 31 for inputting the control signals SDAT, SCLK, and SENB is a configuration block for programmatically controlling the bias of the magnetoresistive head 13 and is configured with a channel and mode selection function. Serial port 31 includes a 4-bit digital-to-analog converter (IDAC). Currents flowing between the PMOS transistor MP6 and the serial port 31 ( , ) Is expressed as the following equation.

4 is a block diagram showing the configuration of a preamplifier connected to a plurality of magnetoresistive heads. Referring to FIG. 4, the preamplifier has a plurality of inputs 14a-14c, a common block 50, a dummy head 42, a serial port and a digital-to-analog converter 31 and a write block 15. One magnetoresistive head is connected to each input unit to form a multi-channel. Referring to the circuit shown in Fig. 2, the input portions 14a to 14c are NPN transistors Q1, Q2, Q11, Q12, Q14, switching means SW1, resistors R10, R11, R13 and An NMOS transistor MN1 is included. Therefore, when the selection signals CSi, i = 1, 2, ... n become logic low, the switching means SWi, i = 1, 2, ... n are activated, and correspondingly to the corresponding magnetoresistive heads. A voltage bias is applied and the preamplifier reads the signal appearing on the magnetoresistive head.

Referring to the circuit illustrated in FIG. 2, the common block 50 includes operational amplifiers gm0, gm1, READ_AMP2 and OPAMP3, NPN transistors Q3, Q4 and Q13, and resistors R1 to R4, R12 and R30. , Current sources I0 to I3, capacitors Cex1 and Cex2, and a programmable voltage controller 25. Inputs 14a-14c and dummy head 42 and common block 50 are connected in parallel to serial port and digital-to-analog converter 31. At this time, when the selection signal CSi is activated as a logic low, the corresponding input unit is activated and thus the signal of the magnetoresistive head connected to the activated input unit is read / write channel (16 in FIG. 1) through the common block 50. Is delivered. As shown in FIG. 4, a multi-channel configuration according to the present invention is possible.

As described above, the preamplifier according to the present invention is a direct current in a stable state corresponding to a change in the internal resistance (Rh) of the magnetoresistive head generated during channel switching, and different internal resistance (Rh) different for each magnetoresistive head manufacturer. The current output offset error is zero to have a high performance, and by adjusting a predetermined number of current sources simultaneously with the control of the magnetoresistive head, there is an effect of realizing a low offset.

Claims (2)

A preamplifier for controlling a magnetoresistive head for reproducing a disk of a hard disk drive, A first feedback circuit for providing a predetermined voltage bias to the regenerative magnetoresistive head and returning a portion of the voltage bias to thereby zero the DC current output offset error to provide a stable voltage bias to the regenerative magnetoresistive head ; A second feedback circuit for feedbacking a part of the voltage bias applied to the reproducing magnetoresistive head to maintain an internal center voltage of the reproducing magnetoresistive head at a ground potential; A programmable voltage controller configured to adjust a magnitude of a voltage bias provided to the regenerative magnetoresistive head; And And an amplifier configured to sense, amplify, and output a signal generated in the magnetoresistive head for reproduction. The hard disk drive of claim 1, wherein a plurality of magnetoresistive heads for reproducing are connected to the preamplifier, and when a selection signal is activated, a signal of a corresponding magnetoresistive head is transmitted to the preamplifier. Preamplification device that controls the magnetoresistive head for playing the disc.