JPS5915505B2 - Temperature compensation circuit for semiconductor resistance effect elements - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a temperature compensation circuit for a semiconductor resistance effect element.

Resistance effect elements made of semiconductor materials change their internal resistance value under the influence of magnetic fields, light rays, pressure, etc. However, these semiconductor materials have a large temperature coefficient, and their output voltage varies greatly depending on the temperature. fluctuate.

3. Moreover, since these semiconductor elements have output characteristics that vary non-linearly with respect to temperature, it is difficult to perform temperature compensation that is suitable for these characteristics. Therefore, as shown in Fig. 1, two semiconductor resistance effect elements 1 and 2 made of the same material are connected in series, and a DC current is passed from a constant voltage power supply 3, and at the same time, resistance effect elements 1 and 2 are connected in series. Temperature compensation is performed by extracting the output from between and canceling out the temperature coefficients of these elements 1 and 2 themselves. However, in the above-mentioned circuit, temperature compensation is performed to a sufficient extent only when fields such as magnetic fields, light rays, or pressure act equally on the two semiconductor resistive elements 1 and 2. If the area or strength acting on one of the resistive effect elements 1 and 2 is biased, in other words, the area or strength on which a magnetic field, light beam, pressure, etc. acts will shift from one element to the other. In the case of a potentiometer that sends out an output that changes according to the ratio, or a switch device or rotation sensor that outputs an output that changes the ratio instantaneously, one resistive effect element is The temperature coefficient of the resistance effect element differs greatly from the temperature coefficient of the other resistance effect element, and the output characteristics are influenced by the element with the larger temperature coefficient, and the same result would be obtained if temperature compensation was not performed.

Therefore, the temperature compensation circuit as shown in FIG. 1 makes the operation of the connected external circuit unstable.

9 These causes will be explained in the case of a magnetoresistive element.

Magnetoresistive elements have a large rate of change with respect to the magnetic field, so
Intermetallic compound semiconductors with high mobility such as InSb, InAs, and InAsP are used as materials, but these have a large temperature dependence as shown in Figure 2.

Generally, in a magnetoresistive element, the internal resistance value Z when there is no magnetic field
(O) becomes Z(O)■Roe-aT, and the internal resistance value Z(B) in the magnetic field is Z
(B)■RoK(B)e-(α+β)T.

Here, Ro is the specific resistance value of the element, (B) is the rate of change of the magnetic field, α is the temperature coefficient in the absence of a magnetic field, β is the temperature coefficient in the presence of a magnetic field, and T is the temperature. FIG. 2 shows the temperature coefficients α, α+β, and β changes with respect to temperature in each equation.

In this figure, the temperature coefficient β is the value when a 5 kilogauss magnetic field is applied to the magnetoresistive element, but in the temperature compensation circuit shown in Fig. 1, the area of the applied magnetic field is large or the magnetic field is strong. The resistor element subjected to this will be greatly influenced by the temperature coefficient β.

Therefore, if the magnetic field acts equally on the pair of magnetoresistive elements 11 and 22, the output characteristics will be flat as shown in FIG. On the other hand, the output decreases as the temperature increases, as shown by curve b.

Conversely, when the magnetic field is biased toward the magnetoresistive element 21, the output becomes lower on the high temperature side as shown by curve c. Therefore, the low temperature (-4'
There is a large difference in output level between the C) side and the high temperature (100°C) side, making it impossible to operate the external circuit stably. Therefore, in recent years, as shown in FIG. 4, a pair of NPN type transistors 4 and PNP type transistors 5 are used, the collectors of each are connected to the positive and negative poles of the power supply 3, and magnetoresistive elements 11 and 21 are connected between the emitters. Connect the series circuit of and also
A bias voltage is applied to the paces of the transistors 4 and 5 from their respective collectors through resistors 6 and 7, and a Zener diode 8 is connected between the bases to magnetically calculate the overall temperature coefficient of the diode 8 and the transistors 4 and 5. Resistance element 1
It has been considered to set the coefficients to be opposite to 1 and 21 to perform temperature compensation of the output.

According to experiments, the maximum temperature compensation error was 20(f) in the temperature range from -4°C to 100°C.

The cause of such an error is that the temperature coefficient of the temperature compensation circuit does not approximate the temperature coefficient change with respect to the magnetic field of the circuit in which the magnetoresistive elements 11 and 21 are read directly in series. The circuit shown in Fig. 4 has an excellent temperature compensation function for the semiconductor resistance effect elements 1 and 2, which have relatively small temperature coefficients, but it is not suitable for semiconductor elements such as InSb, which have a large temperature dependence. was insufficient. The present invention approximates the temperature coefficient of the series circuit of semiconductor resistance effect elements and the temperature coefficient of the drive voltage supplied by the circuit that drives the semiconductor resistance effect element, and thereby suppresses temperature changes regardless of the field conditions acting on the semiconductor resistance effect element. It is an object of the present invention to provide a temperature compensation circuit that obtains flat output characteristics over a wide range. An embodiment of the temperature compensation circuit according to the present invention will be invented using FIG. Semiconductor resistance effect elements 1 and 2 are connected in series, and an output terminal 9 is provided between them. The emitter of a Darlington-connected NPN type first transistor 41 is connected to the resistance effect element 1 . The collectors of the first and second transistors 41 and 42 are connected to the positive electrode of the power supply 3. On the other hand, the resistance effect element 2 is connected to a Darlington-connected PNP type first transistor 5.
1 and connect the emitters of the first and second transistors 51.
, 52 are connected to the negative terminal of the power supply 3. The collector of a third NPN transistor 43 is connected to the positive terminal of the power supply 3, and a fixed bias is applied through a resistor 61. Further, the collector of a PNP type third transistor 53 is connected to the negative electrode of the power source 3, and a constant base potential is applied by a resistor 71. The emitters of the third transistors 43 and 53 are connected to the bases of the second transistors 42 and 52, respectively, and are connected to the first transistors 41 and 41 through variable resistors 62 and 72, respectively.
Connect to the base of 51. Further, the third transistor 43
, 53, a resistor 81 and a positive temperature coefficient thermistor 8 are connected between the emitters of the resistors 81 and 53.
A temperature coefficient setting circuit 80 consisting of two series circuits is connected. In this circuit configuration, the third transistors 43 and 53 fixedly biased by the resistors 61 and 71 have a negative temperature coefficient and a positive temperature coefficient, respectively.

Therefore, as the temperature rises, the potential across the temperature coefficient setting circuit 80 rises. At this time, since the positive temperature coefficient thermistor 82 also increases its internal resistance under the influence of temperature, the voltage across the circuit 80 has a temperature coefficient that is the sum of the temperature coefficients of the transistors 43 and 53 and the temperature coefficient of the thermistor 82. That means that. The Darlington-connected transistors 41, 42 and 51, 52 are operated by the emitter potential of the transistors 43, 53 having this temperature coefficient, but the temperature coefficient is further multiplied by the temperature coefficient of these transistors, and the temperature coefficient of the pair of semiconductors is The temperature coefficient of the voltage applied across the circuit in which the resistance effect elements 1 and 2 are connected in series becomes large.

However, the temperature coefficient of the transistor alone cannot compensate for a circuit having the temperature coefficient curve shown by α+β in FIG. 2 over a wide temperature range.

Therefore, these settings are determined by the temperature coefficient setting circuit 80. For example, in a magnetoresistive element using a semiconductor such as InSb, which has a large temperature dependence, -4'C to 100'C
In the temperature range of
As shown by the solid line in the figure, it is necessary to increase the value rapidly as the temperature increases.

Therefore, in the output characteristic of the temperature compensation circuit shown in FIG. 1, as shown by curve a in FIG. 7, the voltage drop becomes large at high temperatures. Furthermore, in the temperature compensation circuit shown in FIG. 4, the output voltage slightly drops between the low temperature side and the high temperature side, as shown by curve b in the figure. This is because the driving voltage changes linearly as shown by the broken line in FIG. In the temperature compensation circuit of the present invention, as shown by the dotted line in FIG. 6, in order to match the driving voltage with respect to temperature to the curve required by the solid line in the same figure, for example, [〈T1 and t
>T, the voltage gradient of the 1 drive voltage is changed to approximate the actually required curve.

Due to such temperature compensation, the output characteristic becomes a characteristic where two curves join at a certain temperature, as shown in Figure 7c, but compensation near this junction point, for example, near room temperature, becomes extremely accurate. Furthermore, errors in other temperature ranges are also extremely small.

In the temperature compensation circuit of the present invention, a positive temperature coefficient thermistor 82 is used in the temperature coefficient setting circuit 80 as a means for changing the above-mentioned drive voltage gradient.

As shown in FIG. 8, this thermistor exhibits a substantially flat characteristic up to temperature T1, but exhibits a characteristic in which its internal resistance value increases rapidly when the temperature becomes higher than T1. From this, the temperature coefficient setting circuit 80 exhibits the characteristics of the resistor 81 at a temperature lower than T1, and exhibits the characteristics of the thermistor 82 at a temperature higher than T1. The temperature coefficient of the voltage approximates the temperature coefficient of the semiconductor resistance effect elements 1 and 2. In order to make the approximation of the temperature coefficient more accurate, the temperature coefficient setting circuit 80 is constructed by connecting a plurality of compensation elements in series or parallel, as shown in FIG. 8, whose resistance value changes rapidly at different temperatures. do it.

Variable resistors 62 and 72 connected to the Darlington-connected transistors are used to adjust the sensitivity of the drive voltage and at the same time adjust the level of the output characteristics on the low temperature side.

To describe an experimental example of the present invention, InS with a temperature coefficient of 2%/℃
b When a magnetoresistive element is constructed using a semiconductor and a magnetic field of 5 kilogauss is applied, the driving voltage is 0.3 (f)/°C.
required a temperature coefficient of

Therefore, we used a temperature coefficient setting circuit with a 1 kilohm resistor and a temperature coefficient of 40°C.
It is constructed by connecting Murata Manufacturing PTH6OBM6OOM (product name) in series, a positive characteristic thermistor with so-called BM characteristics that exhibits a resistance value of up to 60 ohms and rises rapidly at temperatures above 40°C, and has a temperature range of -406°C to 100°C. When the output characteristics were measured, temperature compensation with a maximum error of less than 1% was obtained. In the embodiment of the present invention, an example in which two semiconductor resistance effect elements are used has been described, but they may be connected consecutively like a three-terminal element.

In this case, the intermediate terminal becomes the output terminal. As described above, according to the temperature compensation circuit of the present invention, stable output characteristics can be obtained even under conditions with large temperature differences, so that the external circuit can operate accurately in response to changes in the semiconductor resistance effect element. As a result, an extremely reliable device can be obtained.

[Brief explanation of the drawing]

Figure 1 is a conventional temperature compensation circuit diagram, Figure 2 is a characteristic diagram of temperature coefficient versus temperature, Figure 3 is an output characteristic diagram using the circuit in Figure 1, and Figure 4 is an improved circuit of Figure 1. FIG. 5 is a temperature compensation circuit diagram showing an embodiment of the present invention, and FIG. 6 is a driving diagram comparing the characteristics of the drive voltage required for temperature compensation with respect to temperature and the characteristics of temperature compensation actually performed. FIG. 7 is an output characteristic diagram comparing the conventional example and the example of the present invention, and FIG. 8 is a characteristic diagram of the resistance change rate with respect to temperature of the compensation element used in the circuit of the present invention. 1, 2... Semiconductor resistance effect element, 9...
・Output terminal, 41, 51... First transistor, 42, 52... Second transistor, 43, 5
3...Third transistor, 62, 72...
... Output characteristic adjustment resistor, 80 ... Temperature coefficient setting circuit, 81 ... Resistor, 82 ... Positive characteristic thermistor.

Claims (1)

[Claims] 1 a set of semiconductor resistance effect elements forming a series circuit;
an output terminal provided between the elements, a power source that supplies current to the element, and a control circuit that is interposed between the power source and the series circuit and provides a drive voltage that has a correlation with the temperature coefficient of the series circuit. A temperature compensation circuit for a semiconductor resistance effect element, comprising: a temperature coefficient setting circuit that operates the control circuit so as to give the drive voltage a coefficient that approximates the temperature coefficient of the series circuit.