JPH09101211A - Temperature compensation circuit for span voltage of semiconductor pressure sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance the work efficiency by disusing the individual adjustment of function trimming and trimming the resistance evenly. SOLUTION: A sensor comprises a gauge part, an amplifier circuit 2, a temperature characteristic compensation circuit 3 for span voltage, and a temperature characteristic compensation circuit 4 at zero point wherein the temperature characteristic compensation circuit 3 for span voltage comprises a thermistor 7, three thick film resistors, a linear positive temperature characteristic resistor, and an operational amplifier. In the temperature characteristic compensation circuit 3 for span voltage, series circuit of the thermistor 7 and a resistor 8 is connected in parallel with a resistor 9 to provide a combined resistor part which is then connected in series with a linear positive temperature coefficient resistor 10 and the joint A of combined resistor part and the linear positive temperature coefficient resistor is connected with the plus terminal of the operational amplifier. On the other hand, a resistor is inserted between a gauge bridge 1 and a ground line and the joint B thereof is connected with the minus terminal of the operational amplifier.

Description

DETAILED DESCRIPTION OF THE INVENTION

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a span voltage temperature compensation circuit for a semiconductor pressure sensor.

2. Description of the Related Art A conventional method for compensating the span voltage and temperature of a semiconductor pressure sensor is to measure the diffusion resistance in an operational amplifier for each sensor as shown in Japanese Patent Application No. 2-135708 and to prepare a thick film corresponding to that value. The resistance is adjusted by function trimming. The span voltage temperature compensation method has a problem that individual measurement and individual adjustment are necessary and work efficiency is not considered.

In order to ensure the accuracy of span voltage temperature compensation, the temperature characteristic of the gauge current is set to the curve positive temperature characteristic.

In a span temperature compensating circuit, a temperature characteristic is made a curve by a combined resistance portion of a thermistor and a thick film resistor, and a positive temperature characteristic is made by a linear positive temperature coefficient resistor. Alternatively, by arranging a parallel thick film resistor in the linear positive temperature coefficient resistor, the curve positive temperature characteristic of the gauge-carrying current can be obtained. By using the span temperature compensation circuit, resistance trimming is uniformly performed, and individual adjustment is abolished. The linear positive temperature coefficient resistor 10 provided in the constant current drive circuit causes the gauge current to have a linear positive temperature characteristic. Further, the thick film resistor 8 is connected in series to the thermistor 7, and the thermistor 7 and the series thick film resistor 8 are connected.
On the other hand, by connecting the combined resistance part in which the thick film resistor 9 is connected in parallel to the linear positive temperature coefficient resistor 10, the linear positive temperature characteristic is bent and the curve positive temperature characteristic is obtained. Thermistor 7
Linear temperature coefficient resistor 10 for thick film resistors without using
By connecting a combined resistance of the parallel thick film resistor 9 and the parallel thick film resistor 9, the curve positive temperature characteristic is similarly obtained.

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below with reference to FIG. The circuit configuration of the pressure sensor is such that a gauge unit 1 for converting a pressure signal into an electric signal, an amplifier circuit 2 constituted by a thick film resistor and an operational amplifier for amplifying a gauge minute voltage signal into a sensor signal, and a span voltage temperature compensation circuit 3 And a zero point voltage temperature compensation circuit 4. The gauge portion 1 is formed of a semiconductor material, for example, silicon into a Wheatstone bridge with four diffusion resistors 5 on the surface. By processing the back surface of the semiconductor material into a diaphragm of several μ, a diaphragm displacement corresponding to the pressure occurs, and two of the four diffusion resistors 5 have a reduced resistance value and the other two have an increased resistance value. By connecting the decreasing resistance and the increasing resistance adjacently, the pressure P6 is applied to the diaphragm.
When is applied, a minute voltage signal corresponding to the applied pressure is generated at the midpoint of the bridge hoiston. Generally, the span temperature change 12 of a gauge for a semiconductor pressure sensor is bad and requires temperature compensation as shown in FIG. In the span voltage temperature compensating circuit 3 of the present invention, a thick film resistor 8 is connected in series to the thermistor 7, and further a linear resistor is provided to a combined resistance portion in which a thick film resistor 9 is connected in parallel to the thermistor 7 and the series thick film resistor 8. The positive temperature coefficient resistor 10 is connected. The junction point A between the combined resistance section and the linear positive temperature coefficient resistor 10 is connected to the positive terminal of the operational amplifier. On the other hand, a resistor is provided between the gauge bridge and the ground line, and the connection point B between the gauge bridge and the resistor is connected to the negative terminal of the operational amplifier. The gauge current 11 has the resistance value of the thermistor 7 and the B constant or the resistance values of the thick film resistors 8 and 9 and the temperature coefficient and resistance of the linear positive temperature coefficient resistor 10 so that the gauge span current 11 has an inverse characteristic of the gauge span temperature change. Obtained by choosing the value appropriately. Next, a second embodiment is shown in FIG.
Will be described. The difference from the first embodiment is that the thermistor 7 and the series thick film resistor 8 are stopped, and the linear positive temperature coefficient resistor 10 and the parallel thick film resistor 9 are arranged. Although the linear positive temperature coefficient resistor 10 has been described in the above description, temperature compensation can be performed by using a diode and a transistor having a positive temperature characteristic. There is no problem even if the thick film resistor is replaced with another resistor such as a thin film resistor. Since the amplifier circuit 2 is not related to the present invention, an example of a one-stage amplifier circuit is shown, but there is no problem even if two or more stages of amplification other than this example are used.

EFFECT OF THE INVENTION Individual gauge characteristic measurement and individual adjustment are abolished in order to compensate the span voltage temperature of the semiconductor pressure sensor, and the span voltage temperature compensation can be dealt with by uniform resistance trimming, so that workability can be improved.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a first embodiment of the present invention.

FIG. 2 is a characteristic diagram of gauge span temperature of a semiconductor pressure sensor.

FIG. 3 is a circuit diagram of a second embodiment of the present invention.

[Explanation of symbols]

1 ... Gauge part, 2 ... Amplification circuit, 3 ... Span voltage temperature compensation circuit, 4 ... Zero point voltage temperature compensation circuit, 5 ... Diffusion resistance, 6
... Applied pressure, 7 ... Thermistor, 8 ... Series resistance, 9 ... Parallel resistance, 10 ... Linear positive temperature characteristic resistor, 11 ... Gauge energization current.

Claims (2)

[Claims] 1. A gauge chip in which at least one diffusion resistor is arranged on a front surface of a semiconductor material substrate, and a back surface of the semiconductor material substrate is processed into a diaphragm, and a temperature compensation circuit and an amplification circuit are formed on a hybrid integrated circuit. In the semiconductor pressure sensor, the gauge drive method is a constant current drive for the span voltage temperature compensation of the semiconductor pressure sensor, and the current-temperature characteristic obtains an inverse characteristic of the gauge span temperature characteristic. A series resistance is connected to at least one parallel resistance at both ends, and a linear positive temperature coefficient resistor is connected in series to connect the series resistance to the linear positive temperature coefficient resistor. Connect the point to the positive terminal of the operational amplifier, provide a resistor between the gauge bridge and the ground line, and connect the gauge bridge and the resistor. Semiconductor pressure sensor span voltage temperature compensation circuit, characterized in configuration of connecting the attachment point to the negative terminal of the operational amplifier. 2. A semiconductor pressure sensor different from claim 1 in that the junction of the operational amplifier to the plus terminal is a resistor, and a junction point A of a combined resistance portion constituted by the parallel positive temperature coefficient resistor and the parallel resistor. Compensation circuit for span voltage.