JPS58118002A - Automatic regularizing circuit for output level of magneto-resistance effect element - Google Patents

Abstract

PURPOSE:To produce an output signal of a certain level with good linearity, by feeding a sense current to a magneto-resistance effect element from a feeding means which is capable of controlling the sense current and at the same time controlling the feeding means in response to the shift value between the output signal level of said effect element and the reference level. CONSTITUTION:A feeding circuit 12 is provided with an output circuit 13, a level detecting circuit 15, an LPF16, a reference level signal supplying circuit 14 and a differential amplifier 17. The output voltage of a magneto-resistance effect element 11 is amplified by an amplifier 13, and the peak level is detected by a detector 15. The differential voltage is delivered from the amplifier 17 between the level of the output signal passed through the LPF16 and the level of the reference level signal supplied from the circuit 14. The differential voltage is converted through a voltage-current converter. For the sense current supplied to the element 11 from the converter 19, the output signal is kept at approximately a certain level regardless of a level change of an applied signal. Furthermore the linearity of the output signal is also improved.

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Technical field of the invention The present invention controls a sense current to obtain linearity and output the sense current.
The present invention relates to an automatic magnetoresistive element output level constantization circuit capable of keeping the output level constant.

(2) Background of the Invention Traditionally, induction type magnetic spatulas P have been used in magnetic recording, but in recent years magnetic heads using magnetoresistive elements have also come into use. Even in this type of head, if the magnetic field applied to the element varies, the output level will vary even if the current flowing through the element is maintained constant.

Since this is not favorable for playback, it is necessary to keep the output level constant.

(3) Prior Art and Problems As a conventional technique for keeping this output level constant, a circuit as shown in FIG. 1 is used.

This circuit uses a magnetoresistive element (fl) and a sense current source (
2), a constant current is passed through the element (1) to generate an output voltage according to the recording magnetic field, and this output voltage is passed through the amplifier (3).
) to the variable gain amplifier (4), and its output level is detected by the level detector (5). Level detector (5
) is passed through a low-pass filter (6) and fed to the other input of a differential amplifier (7) whose reference signal is fed to one input. The gain of the variable gain amplifier (4) is adjusted using the output signal of the variable gain amplifier (4). In this way, even if the recording magnetic field fluctuates, the variable gain amplification W (4)
The output signal, that is, the reproduced output signal, is kept approximately constant.

However, the constancy is obtained by controlling the nonlinear variable gain of the variable gain amplifier (4), and nonlinearity cannot be avoided. Also,
Even if the magnetic field applied to the magnetoresistive element (1) is of sufficient strength, a constant sense current is passed through the magnetoresistive element (1), so the current flowing The smaller the value, the longer the life. Lack of means to extend the life of magnetoresistive elements It is an object of the present invention to provide a magnetoresistive element output and bell constant circuit which can generate an output signal with good linearity at a constant frequency and also extend the life of the magnetoresistive element.

(5) Structure of the Invention The purpose of this invention is to supply a sense current to a magnetoresistive element from a power supply means capable of controlling the sense current, and when the output signal of the magnetoresistive element deviates from the reference level. This is achieved by controlling the power supply means in response to the value and passing a sense current proportional to the value to the magnetoresistive element.

(6) Embodiments of the Invention The present invention will now be described in detail with reference to the attached drawings (11).

FIG. 2 shows a first embodiment of the invention. (10) is a magnetoresistance effect element output level automatic running circuit, which connects a sense current controllable supply \JL@ line (12) to the magnetoresistive element (11), and An output circuit (to) is connected to the output terminal, and in response to the output signal of the output circuit and the reference level signal of the reference level signal supply circuit CI lead, the difference between the reference level signal and the output signal of the output circuit 03) is detected. A corresponding sense current is supplied from the power supply circuit (b) to the element 5-(11).

The output circuit 03) is, for example, a voltage amplifier connected across the element (11).

The power supply circuit 02) is connected to the output circuit 0 as shown in FIG.
A level detection circuit (+5) connected to the output of 3) and a low-pass filter 0 connected to the output of the level detection circuit.
6), and a differential amplifier 0'7) connected to one of the outputs of the filter and having the output of the reference signal supply circuit 04) connected to the other input. The output of the low-pass filter (16) is connected to an operational amplifier through a resistor (+8), which can be controlled by a voltage signal of (21) is connected to the inverting input (-), and the output of the reference level signal supply circuit 0→ is connected to the non-inverting input (+), and a magnetic resistance is connected between the inverting input (-) and the output (22). An effect element 01) is connected and a current proportional to the difference between the reference level signal and the filter output signal representing the level of the output signal of the output circuit Q3) is passed through the element.
- It may be configured as follows.

As is clear from the above, the above-mentioned voltage signal represents the difference between the reference level and the output level, and the voltage-to-current converter (2) that receives this voltage signal converts the above-mentioned difference voltage into its output voltage. It converts into a required current value per unit voltage and supplies this to the element (U).

The operation of the circuit of the present invention having the above configuration will be explained.

The essence of the present invention remains the same, except for the dependence of the resistance value of the magnetoresistive element on the magnetic field between an element using the transverse magnetoresistive effect and an element using the longitudinal magnetoresistive effect, so the following explanation will be given. In this section, an element using the transverse magnetoresistive effect will be explained.

In an element using the transverse magnetoresistive effect, the element resistance value R (H) within the range where the external magnetic field (H) acting on the element is smaller than the magnetic field (H- (see Figure 4) determined by the element) is expressed as In the equation (1), △0+△△ is the element resistance value when the magnetic field is zero, and △R is about 2 to 5% specific to the element (see Fig. 4).

Normally, when a magnetoresistive element is placed in an operating state, a constant ζ ias magnetic field (H) is applied to the element, and a desired signal magnetic field (Δ1- is applied thereto to generate the signal). Whether it is detecting a magnetic field, its signal magnetic field (△■ - △14=hsinwt ・＋＋＋＋＋・＋＋ (
As shown in 2), if the width is sufficiently small and the sense current supplied to the element is 2, then it will be the output from the element. Formula (3)
, the first term is a DC component and the second term is an AC component.

The output voltage of the element (u) expressed by equation (3) is the amplifier (
(3), the peak level is detected by the level detector (15), and the output signal passed through the filter 06) is set to 06, and the amplifier (+:i) and the level detector (1
5), and if the total gain of the filter (]6) is G, then e8-■8. △R0△H0G ,,,,,,,, (
4). However, in formula (4), H*2. The above (θ8) and the reference level signal supply circuit (14)
) is output from the differential amplifier (17).

In the circuit example of Fig. 2, the above-mentioned differential voltage is
111]), the sense 'FM = current (■s) supplied from the converter (111) to the element (11) is 8 = (el
It is expressed as evel-θB door KvI”−−−−−−−(5).If you eliminate 〇 using equations (4) and (5), you get 1+△H・△R−Kv,・q N81evel− −−−−−−−−−−−−=−(6)
(Ura・△)? ,,Kv1. G >> 1). Okay, this relationship can also be obtained with the circuit in Figure 6. This is because if the level of the output signal of the filter (16) is 198, the level of the reference level signal is Elev □, and the resistance value of the resistor (goods) is R, the ton current flowing to the element (11) is as follows. It is.

As is clear from this, even if the applied signal ΔH varies, the output signal is maintained at a substantially constant value. Further, unlike conventional circuits, the output signal is not amplified by a nonlinear variable gain amplifier, so an output signal with good linearity can be obtained. Furthermore, if there is a sufficient signal magnetic field,
Since the sense current is reduced, the device life is also extended.

FIG. 5 shows another embodiment of the present invention, and this embodiment circuit includes a required number of magnetoresistive elements (R.1) to the power supply circuit (b);
(,2), (MB2) (these correspond to each head element of the multi-channel head), except that the amplifier 04) is connected to the appropriate element (MB2). This embodiment is the same as the embodiment shown in FIG. 2, and the same constituent elements are given the same reference characters and their explanations will be omitted. (23) and (24) are amplifiers.

Moreover, the operation and effect are also the same, except for the difference due to the increase in the number of elements.

FIGS. 6 and 7 show, in each of the above embodiment circuits, a current detection means (25) is interposed between the power supply circuit (B) and the element (1υ), and the external magnetic field strength is determined from the display signal. An example of a detection circuit is shown.The current detection means is an ammeter (26) in FIG. 6, a resistor (27) in FIG.
It consists of an amplifier (28) and a display (29).

(A) Effect of the Invention As is clear from the above explanation, according to the present invention, since the sense current is adjusted in response to fluctuations in the output R, the output level is constant and linearity is maintained. Good output signal can be obtained.

Furthermore, since the method controls the sense current, when there is a sufficient external magnetic field, the sense current is also small, resulting in effects such as a longer life of the element.

[Brief explanation of drawings]

FIG. 1 is a conventional circuit diagram, FIG. 2 is an embodiment circuit diagram of the present invention, FIG. 6 is a diagram showing another embodiment circuit of the present invention, FIG. 4 is a resistance value-magnetic field characteristic curve diagram, and FIG. FIG. 5 is a diagram showing still another embodiment of the present invention, and FIGS. 6 and 7 are circuit diagrams for detecting external magnetic field strength. In the figure, (11) is a magnetoresistive element, (b) is a power supply circuit, and (I8) is a voltage signal generation circuit (level detection circuit (1).
5), low pass filter (16), differential amplifier (17)
), (b) are reference level signal supply circuits, 09) are voltage -
The current converter, 2) is a resistor, and (21) is an operational amplifier. Patent applicant Computer Basic Technology Research Association-13- Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7

Claims (1)

[Claims] 1) A power supply circuit capable of controlling a sense current is connected to at least one magnetoresistive element that responds to an external magnetic field, and an output circuit is connected to the output end of the magnetoresistive element, In response to the output signal of the output circuit and the reference level signal of the reference level supply circuit, a sense current corresponding to the difference between the reference level signal and the output signal is transmitted from the power supply circuit to the magnetoresistive element. A magnetoresistance effect element output and an automatic constantization circuit configured to supply R. 2) The power supply circuit is connected to the voltage-current converter connected to the magnetoresistive element, the output of the output circuit, and the output of the reference level supply circuit, and is connected to the voltage-current converter connected to the magnetoresistive element, the output of the output circuit, and the output of the reference level supply circuit. and a voltage signal generation circuit that generates a corresponding voltage signal and supplies it to the voltage-current conversion circuit. circuit. 3) The supply circuit connects the output of the output circuit to the inverting input, and connects the output of the reference level signal supply circuit to the non-inverting large sword. 2. The automatic magnetoresistive element output level stabilization circuit according to claim 1, wherein the circuit is configured to connect an effect element and supply the sense current to the effect element.