磁敏材料及器件霍尔磁阻英课件

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1、Hall effectHall effectThe Static current carrying conductor was put in magnetic fields. When the current direction was inconsistent with the magnetic field direction, on the current-carrying conductor electromotive force was generated between both sides of the parallel current and magnetic field dir

2、ection. The phenomenon was known as the Hall effect. It was Hall electric potential.fl=e B v磁敏材料及器件【霍尔磁阻】【英课件二、二、 The application of Hall sensor1. Hall micro displacement sensor Hall element has the advantages of simple structure, small size, good dynamic characteristics and long life. It is not onl

3、y used to measure the magnetic flux density, active power and energy parameters, but also widely used in the displacement measurement. Fig. 7-12 shows the number of work principle schematic of Hall displacement sensors. Fig.(a) is two identical magnetic field strength permanent magnets, the same pol

4、arity placing opposite, the Hall element being in the middle of two magnets.磁敏材料及器件【霍尔磁阻】【英课件二、二、 The application of Hall sensor1. Hall micro displacement sensorBecause the magnetic induction intensity in the middle of the magnet is B = 0, the Hall potential UH output from Hall element is also zero.

5、 Then the displacement is x = 0. If the Hall element has a relative displacement in the two magnets, the magnetic flux density of the Hall element also will change. Then the UH is not zero, which size will reflect the relative position changes between the Hall element and the magnet. This structure

6、sensor has the dynamic range up to 5 mm, and the resolution is 0.001 mm. 磁敏材料及器件【霍尔磁阻】【英课件UHKxHall elementHall elementHall elementFig.7-12 The working principle of Hall displacement sensor磁敏材料及器件【霍尔磁阻】【英课件 Fig.(b) shows a simple structure Hall displacement sensor, which is a sensor consist of a perm

7、anent magnet magnetic circuit. When x = 0, the Hall voltage is not zero. Fig.(c) is a Hall displacement sensor composed of two same structure magnetic circuits. In order to obtain a better linear distribution, the magnetic pole end is with the pole shoe. Adjusting the initial position of the Hall el

8、ements, Hall voltage is UH = 0. This sensor has a high sensitivity, but the detecting amount of displacement is small. It is suitable for measuring micro-displacement and vibration.磁敏材料及器件【霍尔磁阻】【英课件2. 2. Hall rotate speed sensorHall rotate speed sensor Fig.7-13 is several different structure Hall ro

9、tate speed sensors. The input shaft and the measured shaft of magnetic wheel are connected. When the measured shaft is rotating, the magnetic wheel is rotating therewith. The Hall sensor which is fixed near the magnetic wheel can generate a corresponding pulse by the time each of the small magnet pa

10、ssing. Measuring the number of pulses per unit of time, the measured speed will be obtained. The The number number of of the the small small magnet magnet on on the the magnetic magnetic wheel wheel determines determines rotate rotate speed speed measurement measurement resolution resolution of the

11、sensor.of the sensor.磁敏材料及器件【霍尔磁阻】【英课件1- Input shaft; 2- Rotary table; 3- magnet; 4- Hall sensorFig. 7-13 several structures of Hall rotate speed sensor磁敏材料及器件【霍尔磁阻】【英课件3. Hall Counting Assembly Hall switch sensor SL3501 is an integrated Hall element which has a high sensitivity. It can feel a small

12、 magnetic field change. Thus, it can be used to count the measured black metal parts. Fig.7-14 is a work schematic diagram and circuit diagram of counting ball. When the steel ball passes the Hall switch sensor, the sensor will output pulse voltage of peak 20mV. After the voltage magnifies through t

13、he operational amplifier A (A741), the semiconductor triode VT (2N5812) is driven to work. The output of VT can be connected to the counter for counting, and the measured value is displayed by the displayer.磁敏材料及器件【霍尔磁阻】【英课件steel ballinsulating plateHall switch sensormagnetcounterFig. 7-14 work sche

14、matic and circuit of Hall count devices磁敏材料及器件【霍尔磁阻】【英课件Broken Wire DetectionHall-effectBrokenWireDetectionDevicesteel wire ropeHall elementpermanent magnetamplificationsmoothingcomputerbroken wires signalstocks wave signal磁敏材料及器件【霍尔磁阻】【英课件 Crack Detection of Ferromagnetic MaterialsNS磁敏材料及器件【霍尔磁阻】【英

15、课件Current Sensor When current flows through the wire, a magnetic field will be generated around the wire. The size of the magnetic field is proportional to the current flowing through the wire. The magnetic field can be gathered by soft magnetic materialssoft magnetic materials, then using Hall devi

16、ce for detection.leakage DC Hall sensorDS-50LT series磁敏材料及器件【霍尔磁阻】【英课件 Hall switch integration sensor is a kind of magneto-dependent sensor which is combined the Hall effect with integrated circuit technology. It can perceive everything quantity related to the magnetic information and output it in t

17、he form of switch signal. Hall switch integration sensor has the advantages of long service life, non-contact wear, no spark interference, no conversion jitter, high working frequency, good temperature characteristics and adapting to the harsh environment and so on.Hall Switch Integration Sensor磁敏材料

18、及器件【霍尔磁阻】【英课件 It is consist of the voltage regulator circuit, the Hall element, amplifier, waveshaping circuit and open-circuit output, five parts. Voltage regulator circuit allows the sensor to work in a wide range of supply voltages; open-circuit output allows the sensor to be easily interfaces wi

19、th a variety of logic circuits. 1) Structure and working principle of Hall switch integration sensor磁敏材料及器件【霍尔磁阻】【英课件 磁敏材料及器件【霍尔磁阻】【英课件2) Performance Curve of Hall Switch Integration Sensor As can be seen from the performance curve, the operating characteristic has a certain characteristic hysteresi

20、s BH. The reliability of the switch action is very good. BOP in the figure is the magnetic induction intensity of working point open, and BRP is magnetic induction intensity of the release point off.Performance Curve of Hall Switch Integration SensorVOUT/V12ONOFFBRPBOPBHBTechnical Parameters of Hall

21、 Switch Integration Sensor：working voltage、magnetic induction intensity、output cut-off voltage、 output current flow、operating temperature、operating point.0 The curve shows the relationship between the applied magnetic field and the sensor output level. When the applied magnetic induction intensity i

22、s higher than BOP, the output level is from high to low, and the sensor is in the ON state. When the applied magnetic induction intensity is lower than BOP, the output level is from low to high, and the sensor is in the OFF state.磁敏材料及器件【霍尔磁阻】【英课件3)the application of Hall switch integration sensor （

23、1）interface circuit of Hall switch integration sensor磁敏材料及器件【霍尔磁阻】【英课件General interface circuit of Hall switch integration sensor磁敏材料及器件【霍尔磁阻】【英课件Hall Displacement SensorHall Displacement Sensor Hall displacement sensor can be made into the structure as shown in Fig.(a). A Hall element is placed in

24、the interval between the two opposite polarity and same magnetic field intensity magnetic steels. When the control current I is constant, Hall electric potential UH is proportional to the external magnetic induction intensity. If the magnetic field is within a certain range, the change gradient dB/d

25、x in the x-direction as shown in Fig.(b), is a constant. When the Hall element is moved in the x direction, the change of Hall electric potential should be a constant K (the output sensitivity of the displacement sensor): That is UHKx. It suggests that the Hall electric potential is in a linear rela

26、tionship with displacement. The polarity of output potential reflects the direction of the element displacement. The higher the magnetic field gradient, the greater the sensitivity. the more uniform magnetic field gradient, the better the output linearity. When x0, component is placed in the center

27、of the magnetic field, UH0. This displacement sensor can generally be used to measure tiny displacement of 12mm. It has the characteristics of small inertia, fast response, non-contact measurement. This principle can be used to measure some non-electricity physical quantity, such as force, pressure,

28、 acceleration, liquid level and differential pressure and so on.(a) structure(b) Magnetic field changeFig.9-23 Hall displacement sensor磁敏材料及器件【霍尔磁阻】【英课件二、二、Automobile Hall IgniterAutomobile Hall Igniter The above figure is a schematic diagram of the Hall electronic igniter structure. The Hall elemen

29、t (Fig.3) is fixed on the platinum city of the automobile distributor. A magnetic isolation cover 1 is assembled in the points in the fire. According to the number of automobile engine cylinder, the vertical side of cover leaves evenly spaced gap 2. When the gap is alignment on the Hall element, flu

30、x through by Hall element forms a closed loop circuit. So the circuit is breakover, as shown in the above Fig.(a). the Hall circuit outputs low level (less than or equal to 0.4V). When the bulge part of cover side blocks between the Hall element and the magnets, the circuit is cut-off, as shown in t

31、he above Fig.(b). Hall circuit outputs high level. The principle of Hall electronic igniter is shown below. When the Hall sensor outputs low level, BG1 cut-off, BG2 and BG3 conduction, a constant current will pass the ignition coil primary. When the Hall sensor outputs high level, BG1 conduction, BG

32、2 and BG3 cut-off, the primary current of the igniter is cut-off. In this case, the energy stored in the ignition coil will output as the high pressure discharge form in the secondary lines, namely the discharge ignition. Automobile Hall electronic igniter has the advantage of non-contact, fuel-prud

33、ent, applying to wicked working environment and all kinds of speed, good kaltstartverhalten. At present it has been widely used abroad.Fig. 9-24 Schematic of Hall sensor magnetic circuit1-Magnetic isolation cover 2-gap of magnetic isolation cover 3-Hall element 4-magnetic steel Fig. 9-25 schematic o

34、f Hall electron igniter1-distributor with Hall sensor 2-swutch amplifier 3-ignition coil磁敏材料及器件【霍尔磁阻】【英课件1. Magnetic Resistance Magnetic Resistance is a magneto element based on the magnetoresistive effect, also called MR element. The application range of magnetoresistor is wide. It can be used to m

35、ake magnetic field detector, the displacement and angle detector, the ammeter and the magnetic susceptibility AC amplifier and so on.一、一、Magnetoresistive Effect If the metal for passing a current or the slice of semiconductor material is applied a external magnetic field vertically or horizontally t

36、o the current, its resistance value will increase. Called this phenomenon magnetic resistance effect, magnetoresistance effect for short.磁敏材料及器件【霍尔磁阻】【英课件 Under the applied magnetic field, the Lorentz force of some carrier is larger than the Hall electric field force, so its trajectory is towards th

37、e direction of the Lorentz force. The path of these carriers flowing from one electrode to another electrode is longer than that when no magnetic field, thus, the resistivity increasing. When at a constant temperature, within the magnetic field, the magnetic resistance is in direct proportion to the

38、 square of magnetic induction intensity B. If the device is only in simple cases, electronic involved in conducting, theoretical derivation for the magnetic resistance effect equations asWhere,B the specific resistance when the magnetic induction intensity is B; 0 the specific resistance when the ma

39、gnetic induction intensity is 0; electronic mobility; B the magnetic induction intensity.When the change of the specific resistance is B 0, the relative change of the specific resistance is:Therefore, when a constant magnetic field, the higher the electron mobility of the material (such as InSb, NiS

40、b and InAs semiconductor materials), the more obvious magnetic resistance effect.磁敏材料及器件【霍尔磁阻】【英课件 When there is only a kind of carrier in materials, magnetoresistive effect almost can be ignored. The Hall effect is more strongly. If the electrons and holes are both in the materials (such as InSb),

41、the magnetoresistive effect is very strong. Magnetoresistive effect is also closely related to the shape and size of the magnetic resistor. The magnetoresistive effect related to the size and shape of the magnetic resistance effectmagnetic susceptibility and resistance is called the geometric magnet

42、oresistance effect of magnetoresistive effect. If considering the influence of the shape, the relationship between the relative change of resistivity, magnetic induction intensity and migration rate can be expressed as Rectangle magnetic resistance device is only in the conditions of L(length)b (wid

43、th), it only showes a higher sensitivity. L1). Because the electron movement towards a side, it will inevitably produce Hall effect. When Hall electric field EH forces on electron fE an electric field force is balance to the magnetic field forces on electron a Lorentz force fL, electron trajectory w

44、ill no longer continue to offset. So in the middle of chip, electron movement direction is parallel with the direction of length l, only both ends are tilted. In this situation, the electron motion path increases no significantly, resistance increases not much, too.LbBBGeometric Magnetoresistance Ef

45、fectII（a）（b） Figure(b) is many parallel evenly spaced metal strips (that is, the short-circuit grid) put on Lb rectangle magnetic resistance materials. With short circuit Hall electric potential, this grid magnetic resistance device is shown in figure(b). It is equivalent to many flat strip magnetic

46、 resistance in series. So grid magnetic resistance devices increase resistance under zero magnetic field, also improve the sensitivity of magnetic resistance devices. Experimental results show that, for InSb materials, when B=1T, resistance can be increased 10 times (Because there is no time to form

47、 a larger Hall electric field EH).磁敏材料及器件【霍尔磁阻】【英课件One is on a longer element piece used by vacuum coating method, as shown in figure(a), many short circuit electrode (grating) components.The other is eutectic type semiconductor (when drawn InSb single crystal, adding 1% Ni, it can be obtained InSb

48、and NiSb eutectic material) magnetoresistor made up of InSb and NiSb. In this eutectic, NiSb is a acicular crystal in a certain orientation. It has good electrical conductivity. The diameter of pin is in 1m or so, length approximately 100m. Many of this pins are side-to-side setup, which instead of

49、the effect of metal strip short circuit Hall voltage. Because of the low temperature properties of InSb, it often adds some N type tellurium or selenium to the material, forming doped eutectic. But the sensitivity will be to lose a little. Magnetoresistor is made of a direction to precipitation of m

50、etal in the crystallization process, as shown in the above figure(b).Besides, there is also disc-shaped. There is each an electrode in the center and on the edge, as shown in the above figure(c). Magnetoresistor is mostly made into disk structure.二、二、The structure of Magnetoresistor Magnetoresistor

51、often is used two ways to make:(a)short circuit electrode (c) disk structure(b) precipitated metal directional in the crystals Fig.9-9 the structure of magnetoresistor磁敏材料及器件【霍尔磁阻】【英课件 Various Various shapes shapes of of magnetoresistor, magnetoresistor, the the relationship relationship between bet

52、ween the the magnetic magnetic resistance resistance and and magnetic magnetic induction induction intensity intensity is is shown shown in in the the right right figure. figure. Seeing Seeing from from the the figure, figure, the the magnetic magnetic resistance resistance of of the the disc disc s

53、haped shaped sample is the largest.sample is the largest. The The sensitivity sensitivity of of magnetoresistor magnetoresistor is is generally generally non-linear, non-linear, and and greatly greatly influenced influenced by by the the temperaturetemperature. . Therefore, Therefore, when when usin

54、g using magnetoresistor, magnetoresistor, it it must must first first understands understands the the characteristic characteristic curve curve as as shown shown in in the the figure figure below. below. Then, Then, the the temperature temperature compensation compensation scheme is determined.schem

55、e is determined.Fig. 9-11 the character of magnetoresistor (InSb)magnetic resistanceresistancetemperaturemagnetic fieldsensitivitytemperature characterResistance value of magnetic resistance element has nothing to do with the polarity of the magnetic field. It only increases with the increase of the

56、 magnetic field strengthMagnetic resistance element has a bad temperature characteristic. In the application, it is generally going to design temperature compensation circuitcompensation circuitRelationships with magnetoresistive and magnetic induction磁敏材料及器件【霍尔磁阻】【英课件The Application of Magnetic Sen

57、sitive Resistor:1 as a control element Magnetoresistor can be used in AC converter, frequency converter, voltage converter power voltage transformer, magnetic flux density and the displacement voltage converter and so on, as the control element in circuit .2 as a measure element Magnetoresistor can

58、be used for magnetic field strength measurement, displacement, frequency and power factor measurement, and many other aspects.3 as a switch circuit In close to switch, magnetic card character recognition and magnetoelectric encoder, etc. aspects. 4 as a arithmetic unit Magnetoresistor is available i

59、n multiplier and divider, square, square, cube and use open Fang Qi, etc.5 as a simulation element Used in the nonlinear simulation, simulation, cubic simulation, three times square algebraic expression and negative impedance simulation, etc.磁敏材料及器件【霍尔磁阻】【英课件2. The Application of Magnetoresistor 2.

60、The Application of Magnetoresistor Accordingtothegeomagneticdisturbancefromferromagnetic objects,itcandetectthepresenceofvehicles.Itcanbeusedtoautomatic open thedoor,trafficmonitoring,parkinglot,vehiclelocationmonitoring,trafficlight control and soon.磁敏材料及器件【霍尔磁阻】【英课件 The application of InSb magneto

61、resistive sensor in magnetic ink identifying counterfeit currency count machine InSb counterfeit money detection sensor is installed in light magnetoelectric counterfeit money detection machine. Its working process is shown in the above figure. The schematic diagram of circuit is shown in the figure

62、 below. When magnetic ink on a paper currency is not in position 1, setting the output change is zero. If in position 1, because the R2 resistance increases, the output change is 0.3mV. If in position 3, still is 0. If in position 4, it is -0.3mV. If in position 5, still is zero. Thus, output charac

63、teristic is produced. Through amplified, comparison, pulse broadening, display, it can detect counterfeit money. the ideal effect Is achieved.电路工作原理图InSb伪币检测传感器工作原理与输出特性magnetic printing ink on the paper currencymagnetmagnetoresistoroutput voltagesensoroutputamplific-ationvoltage stabilizercompariso

64、npulse width limitdisplay磁敏材料及器件【霍尔磁阻】【英课件Semiconductor InSb Magnetic Susceptibility Contactless Potentiometer Semiconductor InSb magnetic susceptibility contactless potentiometer is one of the typical applications in semiconductor InSb magnetoresistive effect. Compared with the traditional potentio

65、meter, it has incomparable advantages: no contact brush, no electrical contact noise, rotating torque is small, high resolution, good frequency characteristic, high reliability, long service life. Semiconductor InSb magnetic susceptibility contactless potentiometer is based on the principle of semic

66、onductor InSb magnetoresistive effect. It is consist of the semiconductor InSb magnetic susceptibility resistance element and bias magnetic steel. Its structure is similar to the ordinary potentiometer. Due to no brush contact, therefore it is called contactless potentiometer. The core of the potent

67、iometer is difference type structure of the two semicircle magnetoresistors. They are installed on the same axis of the semicircle permanent magnet steel. Its area is just right to cover one of the magnetoresistors. As the rotation axis is turnning, the area of the magnetic resistance elements cover

68、ed by magnetic steel will change. Then the magnetoresistors resistance value changes, rotating axis, which can adjust the resistance value. The relation curve between working principle and the output voltage changing with rotation angle is shown in figure.磁敏无接触电位器工作原理示图和输出特性曲线090-90angle磁敏材料及器件【霍尔磁阻

69、】【英课件3. Magnetodiode and Magnetic susceptibility triode Magnetodiode and triode are new magnetoelectricity conversion components after the development of Hall elements and magnetoresistors. Hall elements and magnetoresistors are body elements both made up of N type semiconductor materials. Magnetodi

70、ode and magnetic susceptibility triode are the magnetoelectricity conversion components in PN junction type. They have the advantages of output signal, high sensitivity (magnetic sensitivity is higher than hall element hundreds or even thousands of times), small working current, can identify the pol

71、arity of the magnetic field, small volume, simple circuit. They are suitable for magnetic field, rotating speed flaw detection and control, etc.磁敏材料及器件【霍尔磁阻】【英课件一、一、The Structure and Principle of Magnetodiode1Structure P-type and N-type electrode of magnetodiode is made of high resistance materials.

72、 Between P and N, there is a longer intrinsic region I. One side of the intrinsic area I is grinded to a smooth lower composite surface(for I region). The other side is grinded to ground, which is set to high composite(r region). Its purpose is that because electron-hole easily vanish in rough surfa

73、ce composite. When through the forward current, it will be formed current among P, I and N junction. Therefore, magnetodiode is the PIN type.areastructuresymbolFig. 9-12 schematic of magnet sensing diode structure磁敏材料及器件【霍尔磁阻】【英课件 When magnetodiode is not subjected to the external magnetic field, pl

74、us a positive bias (P region is positive), there are a lot of holes moving from P region through I region entering N region. At the same time, there are a large number of electron injection P region, thus a current from. Only a small number of electrons and holes in region I are compound. When magne

75、todiode is forced external magnetic field H+ (positive magnetic field) shown in the following figure(b), the electrons and holes are forced Lorentz force then deflection to r region. Due to the compound speed of electrons and holes in r region is faster than the smooth surface I region, once holes a

76、nd electrons composite, it will lead to losing conductive mechanism. It means that the equivalent resistance of base region increases, current decreases. The stronger the magnetic field intensity, the Lorentz force of electrons and holes is greater. Per unit time due to into r region, the number of

77、composite electrons and holes is more. Carrier decreases, and the external circuit current is smaller. When magnetodiode is forced by external magnetic field H-(reverse magnetic field) as shown in the right figure(c), the electrons and holes by Lorentz force will migrate to the region I. Because the

78、 recombination rate of electron and hole decreases significantly, the region i the equivalent resistance will reduce, and the external circuit current becomes larger. If the reverse bias (negative of P region) is added to the magnetodiode, there is only a very small current passing through, and almo

79、st it has nothing to do with the magnetic fields. Therefore, the device can only work under forward bias. Using the characteristics of magnetodiode of forward direction guide current changing along with the change of magnetic field intensity, magnetoelectricity conversion can be realized.surfacesurf

80、acesurfaceschematic of magnet sensing diode work principle磁敏材料及器件【霍尔磁阻】【英课件Conclusion: As the change of the size and direction of magnetic field, it can produce the change of positive and negative output voltage. Especially under the effect of weak magnetic field, the larger output voltage can be ob

81、tained. If out of region r and r, the greater the difference of composite ability, the higher sensitivity of the magnetodiode. While the magnetodiode is reverse biased, there is only a very small current through r region, almost having nothing to do with the magnetic field. Therefore, on both ends o

82、f the diode the voltage will not be any changed by the magnetic field effect.磁敏材料及器件【霍尔磁阻】【英课件3The Key Property of Magnetodiode(1) Magnetoelectric Properties Under the given conditions, the relationship between output voltage variation of the magnetodiode and the magnetic field is called the magneto

83、electric properties of magnetodiode. There are usually single and complementary two ways to use magnetodiode. The magnetoelectric properties are shown in the figure below. The figure shows that when single used only, the forward magnetic sensitivity is greater than the reverse. When complementary us

84、ed, positive and reverse magnetic sensitivity curve is symmetrical. There is a good linear under weak magnetic field.when using a singlecomplementary when usingFig. 9-14 magnetoelectric properties 磁敏材料及器件【霍尔磁阻】【英课件(2) Volt-ampere Characteristics The relationship between forward biased of magnetodiod

85、e and current is called the volt-ampere characteristic of magnetodiode, as shown in figure. From the figure, the magnetodiode under different magnetic field intensity H, the volt-ampere characteristics will be different. Figure (a) is the volt-ampere characteristics of germanium magnetodiode. (b) is

86、 silicon magnetodiode volt-ampere characteristics. Figure (b) showed that in a wider range of bias, current change is relatively smooth. When the applied bias increases to a certain value, the current will increase rapidly, and volt-ampere characteristics curve rises quickly, which shows that its dy

87、namic resistance is small.The volt-ampere characteristics of germanium magnetic susceptibilityThe volt-ampere characteristics of silicon magnetic susceptibilityThe volt-ampere characteristics of magnetic susceptibility磁敏材料及器件【霍尔磁阻】【英课件(3) Temperature Characteristic Under normal circumstances, the ma

88、gnetodiode is greatly influenced by temperature. In some test conditions, the output voltage change of the magnetodiode U, or in the absence of magnetic field effect, change with the temperature of midpoint voltage Um is bigger. In actual use, therefore, there must be temperature compensation. Compl

89、ementary Temperature Compensation Circuit Choosing two similar performance magnetodiodes, opposite magnetic polarity is combined. That is their magnetic susceptibility surface relative or backput in the tandem connection circuit. No matter how changes in temperature, the partial of pressure always r

90、emains the same. Output voltage Um changes with the temperature and always remains the same, so that the purpose of temperature compensation is realized. Not only that, but complementary circuit can improve the magnetic sensitivity.Fig.9-16 When using a single magnetic susceptibility diode temperatu

91、re characteristicback to joincompensating circuit(a)equivalent circuit磁敏材料及器件【霍尔磁阻】【英课件 Differential Circuit Shown in the figure(c) below. Differential circuit can not only well realize temperature compensation, improve the sensitivity, but also make up for the inadequacy of complementary circuit. I

92、f circuit not balance, it can be appropriately adjust resistors R1 and R2. Full-Bridge Circuit The full-bridge circuit is parallel with two complementary circuits. As well as complementary circuit, its working point can only be selected in the small current region. The circuit in a given magnetic fi

93、eld, the output voltage is double that of the differential circuit. Due to need to choose four same performance magnetodiodes, It will bring some difficulties to actual use. Thermistor Compensation Circuit As shown in the figure(e) below. This circuit makes the use of thermistor change with temperat

94、ure. The partial coefficient of pressure of Rt and D are unchanged, so as to realize temperature compensation. Thermistor compensation circuit is slightly lower than the cost of the above three kinds of temperature compensation circuit. So it is often used in a temperature compensation circuit.磁敏材料及

95、器件【霍尔磁阻】【英课件二二、The Working Principle and Structure of Magnetic Susceptibility Triode1Structure of Magnetic Susceptibility Triode Emitter, the base and the collector are formed in weak P type or weak N type intrinsic semiconductor by alloyage or diffusion process. The biggest characteristic is the lo

96、nger base region. The base region structure is similar to magnetodiode. Also it has a high compound rate of r region and intrinsic I region. Long base region is divided into transport base region and composite base region. 2The Working Principle of Magnetic Susceptibility Triode When the magnetic su

97、sceptibility triode is not under magnetic field effect, because the base region width is greater than the effectively diffusion length of carrier, most of the carriers are through the e-I-b, forming the base current. The minority carriers input to c pole, thus base current is greater than the collec

98、tor current. When under the positive magnetic field (H+), as the action of magnetic field, the Lorentz force makes the carrier deflection to composite region. The collector current significantly reduces. When under the reverse magnetic field (H-), carrier deflection to the collector side, it makes c

99、ollector current increasing. Therefore, magnetic susceptibility triode in the role of positive and reverse magnetic field, the collector current apparently changes.structure (NPN)(b) symbolFig.9-18 structure and symbols of the magnetic-sensitive transistor composite base regionThe base transportFig.

100、9-19 work principle of the magnetic-sensitive transistor 磁敏材料及器件【霍尔磁阻】【英课件N+N+N+cccyyyeeerrrxxxP+P+P+bbbN+N+N+（a）（b）（c）Fig. 2.6-34 schematic of the magnetic-sensitive transistor work principle (a)H=0; (b)H=H+;(c)H=H-1-The base transport；2-composite base region12磁敏材料及器件【霍尔磁阻】【英课件3. Key Property of Ma

101、gnetic Susceptibility Triode(1) Magnetoelectric Properties The magnetoelectric properties of magnetic susceptibility triode is the basis of the application, and is one of the main features. For example, magnetoelectric properties of domestic NPN 3BCM (Ge) magnetic susceptibility triode, under the ef

102、fect of weak magnetic field, the curve is close to a straight line, as shown in the left down figure.(2) Volt-ampere Characteristics Volt-ampere characteristics of magnetic susceptibility triode is similar to ordinary transistor volt-ampere characteristic curve. Down right figure(a) is, when not aff

103、ected by magnetic field, the volt-ampere characteristic curve of magnetic susceptibility triode. Down right figure(b) is, when the magnetic field 1kGs, base current 3mA, the change of the collector current. By the figure, current magnification times of the magnetic susceptibility triode is less than

104、 1.magnetoelectric properties of 3BCMvolt-ampere characteristics of the magnetic-sensitive transistor磁敏材料及器件【霍尔磁阻】【英课件(3) Temperature Characteristic and its Compensation Magnetic susceptibility triode is more sensitive to temperature. When actual use, it must adopt the appropriate methods for temper

105、ature compensation. For germanium magnetic susceptibility triode, for example, 3ACM and 3BCM, its temperature coefficient of the magnetic sensitivity is 0.8/. Silicon magnetic susceptibility triode (3CCM), temperature coefficient of magnetic sensitivity is -0.6/. For silicon magnetic susceptibility

106、triode, ordinary silicon triode with the positive temperature coefficient can be used to compensate for the collector current drift from temperature. Compensation circuit is shown in figure (a). When temperature increases, collector current Ic of BG1 tube will increase, which leads to collector curr

107、ent of BGm tube also increases. Thus, BGm tube temperature increase leading to a decline in Ic is compensated. Figure (b) is the use of germanium magnetodiode current increasing with temperature rising, and make it as a load of the silicon magnetic susceptibility triode. When the temperature rises,

108、it can compensate for the negative temperature drift coefficient of silicon magnetic susceptibility triode caused the current decline. In addition, also two magnetic susceptibility triodes with consistent characteristics and alternating polarity are consist of a difference circuit, as shown in figur

109、e (c). The circuit not only can improve the magnetic sensitivity, but also can realize the temperature compensation. It is an effective temperature compensation circuit.temperature-compensation circuit of the magnetic-sensitive transistor磁敏材料及器件【霍尔磁阻】【英课件（三）（三）The Application of Magnetodiode and Mag

110、netic Susceptibility Triode Because the magnetic susceptibility tube has a higher magnetic sensitivity, volume and power consumption are small, and it can identify magnetic polarity. It is a new type of semiconductor magneto sensor, and it has a broad application prospect. Using magnetic susceptibil

111、ity tube can makesuch as Gauss Meter, Leakage Flux Measuring Instrument, Geomagnetism Detection Instrument, etc. Using magnetic susceptibility tube is made of magnetic field detector, and it can measure weak magnetic field around 10-7T. According to the magnetic field around the wire, the strength o

112、f the magnetic field depends on the current size in the wire. By the use of magnetic susceptibility tube, non-contact method is used to measuring current in the wire. This device not only can detect the magnetic field, but also can determine the current value size of wire. It is both safe and save e

113、lectricity. Therefore, it is a kind of popular current meter. In addition, the use of magnetic susceptibility tube also can make into rotational speed sensor (can measure the speed up to tens of thousands of revolutions per minute), non-contact potentiometer and leakage flux flaw detector, etc.磁敏材料及

114、器件【霍尔磁阻】【英课件Magnetodiode Leakage Magnet Flaw Detector Magnetodiode leakage magnet flaw detector make the use of magnetodiode detecting weak magnetic field change. Principle is shown as the figure. leakage magnet flaw detector is consist of the exciting coil 2, iron core 3, amplifier 4, magnetodiode

115、probe 5, etc. Determinand 1 (such as steel bar) is put under the iron core, and constantly rotating, after the iron core and coil exciting, steel bar is magnetized. If no damage part of the under test steel bar is under the iron core, the magnetized parts of iron core and steel bar constitute a clos

116、ed magnetic circuit. Exciting coil induction flux is , and at this time there is no leakage magnetic flux. magnetodiode probe is no signal output. If the cracks on the steel bar spin to the core, at the crackle the leakage magnetic flux effects on the probe. The probe will put the leakage magnetic f

117、lux converted into voltage signal, through amplifier the output amplification. According to the value of the indicating instrument, the defects of under test iron bars are obtained.Fig. 9-26 work principle of the leakage magnetic flow detectorcrackdisplay instrumentdisplay instrument磁敏材料及器件【霍尔磁阻】【英课件A Few Useful Conceptprecision（accuracy）sensitivityresolutionstability （long-term 、 short-term）measurement dynamic range （range）磁敏材料及器件【霍尔磁阻】【英课件