JPH0668403A - Magneto-resistance element driving circuit - Google Patents
Magneto-resistance element driving circuitInfo
- Publication number
- JPH0668403A JPH0668403A JP21897092A JP21897092A JPH0668403A JP H0668403 A JPH0668403 A JP H0668403A JP 21897092 A JP21897092 A JP 21897092A JP 21897092 A JP21897092 A JP 21897092A JP H0668403 A JPH0668403 A JP H0668403A
- Authority
- JP
- Japan
- Prior art keywords
- magnetoresistive element
- magneto
- equation
- transistor
- change
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
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- Recording Or Reproducing By Magnetic Means (AREA)
- Magnetic Heads (AREA)
Abstract
Description
【０００１】[0001]
【産業上の利用分野】本発明は磁気抵抗素子を用いた磁
気記録再生回路における磁気抵抗素子駆動回路に関する
ものである。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetoresistive element driving circuit in a magnetic recording / reproducing circuit using a magnetoresistive element.
【０００２】[0002]
【従来の技術】近年、デジタルコンパクトカセット（以
下ＤＣＣと呼ぶ）に代表されるように、磁気抵抗素子を
用いたデジタル磁気記録再生装置が商品化されてきてい
る。2. Description of the Related Art In recent years, a digital magnetic recording / reproducing apparatus using a magnetoresistive element has been commercialized as represented by a digital compact cassette (hereinafter referred to as DCC).
【０００３】このような機器において、磁気抵抗素子は
媒体に記録された磁化を抵抗変化に変換する素子であ
る。この抵抗変化を電圧変化に変換する手段として磁気
抵抗素子駆動回路がある。In such a device, the magnetoresistive element is an element that converts the magnetization recorded in the medium into a resistance change. There is a magnetoresistive element drive circuit as a means for converting this resistance change into a voltage change.
【０００４】以下に、従来の磁気抵抗素子駆動回路の一
例について説明する。図２はこの従来の磁気抵抗素子駆
動回路のブロック図を示すものである。図２において、
１は抵抗値Ｒmの磁気抵抗素子、３は再生信号の出力端
子、Ｒ３，Ｒ４及びＲ５はそれぞれ抵抗値Ｒ３，Ｒ４及
びＲ５の抵抗、Ｑ１はトランジスタ、５は電圧値Ｖの電
源である。An example of a conventional magnetoresistive element drive circuit will be described below. FIG. 2 shows a block diagram of this conventional magnetoresistive element drive circuit. In FIG.
Reference numeral 1 is a magnetoresistive element having a resistance value Rm, 3 is a reproduction signal output terminal, R3, R4 and R5 are resistors having resistance values R3, R4 and R5, Q1 is a transistor, and 5 is a power source having a voltage value V.
【０００５】以上のように構成された磁気抵抗素子駆動
回路について、以下その動作について説明する。The operation of the magnetoresistive element drive circuit configured as described above will be described below.
【０００６】磁気抵抗素子１は磁気媒体（図示せず）上
の記録磁化の微小変化ｄＨに応じて抵抗値Ｒmが変化す
る。The resistance value Rm of the magnetoresistive element 1 changes in accordance with a minute change dH in recording magnetization on a magnetic medium (not shown).
【０００７】Ｒmの変化ｄＲm／ｄＨは（数１）で決まる
電流Ｉsにより電圧値の変化Ｉs＊ｄＲm／ｄＨに変換さ
れる。The change dRm / dH in Rm is converted into a change in voltage value Is * dRm / dH by the current Is determined by (Equation 1).
【０００８】[0008]
【数１】 [Equation 1]
【０００９】電圧値の変化はトランジスタＱ１のベース
に入力され、抵抗Ｒ４及びＲ５で決まる所定の増幅がな
されて出力端子３に出力される。The change in voltage value is input to the base of the transistor Q1, amplified by a predetermined amount determined by the resistors R4 and R5, and output to the output terminal 3.
【００１０】結局、磁気媒体上の記録磁化の微小変化ｄ
Ｈに対して出力端子３に現れる電圧Ｅの変化ｄＥ／ｄＨ
は、トランジスタＱ１のベース入力インピーダンスを∞
とした場合、（数２）で与えられる。ただし、γは磁気
抵抗素子１で決まる定数である。After all, a small change d in the recording magnetization on the magnetic medium
Change in voltage E appearing at output terminal 3 with respect to H dE / dH
Is the base input impedance of the transistor Q1
Is given by (Equation 2). However, γ is a constant determined by the magnetoresistive element 1.
【００１１】[0011]
【数２】 [Equation 2]
【００１２】以下、ｄＥ／ｄＨを感度と呼ぶ。Hereinafter, dE / dH is referred to as sensitivity.
【００１３】[0013]
【発明が解決しようとする課題】しかしながら上記の従
来の構成では、磁気抵抗素子１の温度特性等により抵抗
値Ｒmが経時的に変化した場合、トランジスタＱ１のベ
ース電位が変化し、出力端子３の電位が変化してしま
う。出力端子３の電位が安定しないと、以降の回路設計
が非常に難しくなり回路規模が増大する。However, in the above conventional configuration, when the resistance value Rm changes with time due to the temperature characteristics of the magnetoresistive element 1, the base potential of the transistor Q1 changes, and the output terminal 3 of the output terminal 3 changes. The electric potential changes. If the potential of the output terminal 3 is not stable, subsequent circuit design becomes very difficult and the circuit scale increases.
【００１４】また、（数２）から明らかなように、感度
ｄＥ／ｄＨが電源５の電圧値Ｖに依存するため、電源電
圧変動に対し安定した動作が得られないという問題点を
有していた。Further, as is clear from (Equation 2), since the sensitivity dE / dH depends on the voltage value V of the power supply 5, there is a problem in that stable operation cannot be obtained against fluctuations in the power supply voltage. It was
【００１５】本発明は上記従来の問題点を解決するもの
で、磁気抵抗素子１の抵抗値Ｒmの経時変化が出力端子
３の電位に影響せず、かつ電源電圧変動に対し安定した
動作を得る磁気抵抗素子駆動回路を提供することを目的
とする。The present invention solves the above-mentioned problems of the prior art, and the change over time of the resistance value Rm of the magnetoresistive element 1 does not affect the potential of the output terminal 3, and a stable operation is obtained against fluctuations in the power supply voltage. An object is to provide a magnetoresistive element drive circuit.
【００１６】[0016]
【課題を解決するための手段】この目的を達成するため
に本発明の磁気抵抗素子駆動回路は、第１の磁気抵抗素
子と、第２の磁気抵抗素子と、トランジスタと、電圧源
とで構成され、第１の磁気抵抗素子の一方の端子をトラ
ンジスタのエミッタに接続し、第２の磁気抵抗素子の一
方の端子をトランジスタのコレクタに接続し、電圧源の
出力をトランジスタのベースに接続している。In order to achieve this object, a magnetoresistive element drive circuit of the present invention comprises a first magnetoresistive element, a second magnetoresistive element, a transistor and a voltage source. One terminal of the first magnetoresistive element is connected to the emitter of the transistor, one terminal of the second magnetoresistive element is connected to the collector of the transistor, and the output of the voltage source is connected to the base of the transistor. There is.
【００１７】[0017]
【作用】本発明は上記した構成によって、出力端子の電
位はトランジスタのコレクタ電位で与えられ、コレクタ
電流と第２の磁気抵抗素子の抵抗値の積で決まる電圧降
下を電源電圧から差し引いたもので与えられる。一方、
コレクタ電流は第１の磁気抵抗素子の抵抗値に反比例す
る。すなわち、トランジスタのコレクタ電位は磁気抵抗
素子の抵抗値変化に対し負帰還が与えられるように動作
する。According to the present invention, the potential of the output terminal is given by the collector potential of the transistor, and the voltage drop determined by the product of the collector current and the resistance value of the second magnetoresistive element is subtracted from the power supply voltage. Given. on the other hand,
The collector current is inversely proportional to the resistance value of the first magnetoresistive element. That is, the collector potential of the transistor operates so that negative feedback is given to the change in the resistance value of the magnetoresistive element.
【００１８】[0018]
【実施例】以下、本発明の一実施例について、図面を参
照しながら説明する。DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.
【００１９】図１は本発明の実施例における磁気抵抗素
子駆動回路の回路図を示すものである。図１における
３，５及びＱ１については図２の従来例と同じであるの
で説明は省略する。１は抵抗値Ｒm1の第１の磁気抵抗素
子、２は抵抗値Ｒm2の第２の磁気抵抗素子、Ｒ１は抵抗
値Ｒ１の抵抗、Ｒ２は抵抗値Ｒ２の抵抗、４は抵抗Ｒ１
及びＲ２で構成される電圧源である。FIG. 1 is a circuit diagram of a magnetoresistive element drive circuit according to an embodiment of the present invention. Since 3, 5 and Q1 in FIG. 1 are the same as those in the conventional example of FIG. Reference numeral 1 is a first magnetoresistive element having a resistance value Rm1, 2 is a second magnetoresistive element having a resistance value Rm2, R1 is a resistance value R1, R2 is a resistance value R2, and 4 is a resistance R1.
And R2.
【００２０】電圧源４の電圧値Ｖrefは電源５の電圧
Ｖ、抵抗Ｒ１及びＲ２の抵抗値Ｒ１及びＲ２より（数
３）で与えられる。The voltage value Vref of the voltage source 4 is given by (Equation 3) from the voltage V of the power source 5 and the resistance values R1 and R2 of the resistors R1 and R2.
【００２１】[0021]
【数３】 [Equation 3]
【００２２】出力端子３の電位ＥはトランジスタＱ１の
コレクタ電位と同じで、（数４）できまる。ただし、ｈ
FEはトランジスタＱ１の順方向電流増幅率である。The potential E of the output terminal 3 is the same as the collector potential of the transistor Q1 and can be calculated by (Equation 4). However, h
FE is the forward current amplification factor of the transistor Q1.
【００２３】[0023]
【数４】 [Equation 4]
【００２４】まず、第１の磁気抵抗素子１の抵抗値と第
２の磁気抵抗素子２の抵抗値を同じ値に選んだ場合を考
える。Ｒm1＝Ｒm2で、このとき（数４）は（数５）の如
く変形できる。First, consider a case where the resistance value of the first magnetoresistive element 1 and the resistance value of the second magnetoresistive element 2 are selected to be the same value. Rm1 = Rm2, and then (Formula 4) can be transformed into (Formula 5).
【００２５】[0025]
【数５】 [Equation 5]
【００２６】すなわち、この場合、コレクタ電位は磁気
抵抗素子の抵抗値の関数でなくなり、磁気抵抗素子の抵
抗値の経時変化に対し出力端子３の電位は安定する。That is, in this case, the collector potential is not a function of the resistance value of the magnetoresistive element, and the potential of the output terminal 3 is stable against the change with time of the resistance value of the magnetoresistive element.
【００２７】つぎに、第１及び第２の磁気抵抗素子１，
２それぞれの抵抗値が異なる場合を考える。一般的に、
磁気抵抗素子の抵抗値の経時変化の主要因として温度特
性が挙げられる。第１の磁気抵抗素子１の抵抗値の温度
特性をｄＲm1／ｄＴ、第２の磁気抵抗素子２の抵抗値の
温度特性をｄＲm2／ｄＴで表現する。出力端子３の温度
特性ｄＥ／ｄＴは（数４）を偏微分することで（数６）
で表される。Next, the first and second magnetoresistive elements 1,
2 Consider a case where the respective resistance values are different. Typically,
The temperature characteristic is a main factor of the change in resistance value of the magnetoresistive element with time. The temperature characteristic of the resistance value of the first magnetoresistive element 1 is represented by dRm1 / dT, and the temperature characteristic of the resistance value of the second magnetoresistive element 2 is represented by dRm2 / dT. The temperature characteristic dE / dT of the output terminal 3 is obtained by partially differentiating (Equation 4) (Equation 6).
It is represented by.
【００２８】[0028]
【数６】 [Equation 6]
【００２９】（数６）をｄＥ／ｄＴ＝０とおくことで、
（数７）が導出される。By setting (Equation 6) as dE / dT = 0,
(Equation 7) is derived.
【００３０】[0030]
【数７】 [Equation 7]
【００３１】（数７）を満足する様に第１及び第２の磁
気抵抗素子１，２を選べば、出力端子３の電位は温度に
依存しないことは明らかである。If the first and second magnetoresistive elements 1 and 2 are selected so as to satisfy (Equation 7), it is clear that the potential of the output terminal 3 does not depend on temperature.
【００３２】一方、磁気媒体上の記録磁化の微小変化ｄ
Ｈに対して出力端子３に現れる電圧Ｅの変化ｄＥ／ｄＨ
すなわち感度は、トランジスタＱ１のベース入力インピ
ーダンスを∞とした場合、（数８）で与えられる。ただ
し、γ1は第１の磁気抵抗素子１で決まる定数、γ2は第
２の磁気抵抗素子２で決まる定数である。On the other hand, a minute change d in the recording magnetization on the magnetic medium
Change in voltage E appearing at output terminal 3 with respect to H dE / dH
That is, the sensitivity is given by (Equation 8) when the base input impedance of the transistor Q1 is ∞. However, γ1 is a constant determined by the first magnetoresistive element 1, and γ2 is a constant determined by the second magnetoresistive element 2.
【００３３】[0033]
【数８】 [Equation 8]
【００３４】感度ｄＥ／ｄＨが電源５の電圧値Ｖに依存
しないことは（数８）より明らかである。It is clear from (Equation 8) that the sensitivity dE / dH does not depend on the voltage value V of the power supply 5.
【００３５】また、第１の磁気抵抗素子１の磁化の微小
変化に対する抵抗変化の極性を第２の磁気抵抗素子２の
それに対し逆にすることで、差動駆動が可能である事は
言うまでもない。Further, it goes without saying that the polarity can be differentially driven by reversing the polarity of the resistance change with respect to the minute change of the magnetization of the first magnetoresistive element 1 to that of the second magnetoresistive element 2. .
【００３６】また、第１及び第２の磁気抵抗素子１，２
のいずれか一方を、磁化の微小変化に対する抵抗変化を
ほぼ０にして使用しても同様の効果が期待できる。磁化
に対する抵抗変化をほぼ０にするには、磁気抵抗素子に
所定の直流磁界を与える事で容易に実現できる。The first and second magnetoresistive elements 1 and 2 are also provided.
The same effect can be expected by using either one of them with the change in resistance to a minute change in magnetization set to almost zero. It is easy to make the change in resistance to magnetization almost zero by applying a predetermined DC magnetic field to the magnetoresistive element.
【００３７】[0037]
【発明の効果】以上のように本発明によれば、磁気抵抗
素子の抵抗値が経時的に変化した場合でも、出力端子の
電位は安定するので、以降の回路設計が非常に簡易にな
り、回路規模を大幅に削減できる。また、感度が電源電
圧に依存しないので電源電圧変動に対し常に安定した動
作が得られ、実用上極めて有用である。As described above, according to the present invention, even if the resistance value of the magnetoresistive element changes with time, the potential of the output terminal is stable, so that the subsequent circuit design becomes very simple. The circuit scale can be significantly reduced. Further, since the sensitivity does not depend on the power supply voltage, stable operation can be always obtained against fluctuations in the power supply voltage, which is extremely useful in practice.
【図１】本発明の実施例における磁気抵抗素子駆動回路
の構成を示す回路図FIG. 1 is a circuit diagram showing a configuration of a magnetoresistive element drive circuit according to an embodiment of the present invention.
【図２】従来の磁気抵抗素子駆動回路の構成を示す回路
図FIG. 2 is a circuit diagram showing a configuration of a conventional magnetoresistive element drive circuit.
１ 第１の磁気抵抗素子 ２ 第２の磁気抵抗素子 ３ 出力端子 ４ 電圧源 ５ 電源 Ｑ１ トランジスタ 1 1st magnetoresistive element 2 2nd magnetoresistive element 3 output terminal 4 voltage source 5 power supply Q1 transistor
Claims (1)
を電源の一方に接続した第１の磁気抵抗素子と、 一端を上記トランジスタのコレクタに、他端を上記電源
の他方に接続した第２の磁気抵抗素子と、 上記トランジスタのベースに接続した電圧源と、を備え
た磁気抵抗素子駆動回路。1. A first magnetoresistive element having one end connected to the emitter of the transistor and the other end connected to one of the power supplies; and a second magnetoresistive element having one end connected to the collector of the transistor and the other end connected to the other of the power supplies. A magnetoresistive element drive circuit comprising a magnetoresistive element and a voltage source connected to the base of the transistor.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP21897092A JPH0668403A (en) | 1992-08-18 | 1992-08-18 | Magneto-resistance element driving circuit |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP21897092A JPH0668403A (en) | 1992-08-18 | 1992-08-18 | Magneto-resistance element driving circuit |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPH0668403A true JPH0668403A (en) | 1994-03-11 |
Family
ID=16728218
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP21897092A Pending JPH0668403A (en) | 1992-08-18 | 1992-08-18 | Magneto-resistance element driving circuit |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH0668403A (en) |
-
1992
- 1992-08-18 JP JP21897092A patent/JPH0668403A/en active Pending
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