JPS6325525A - Semiconductor pressure sensor - Google Patents

Abstract

PURPOSE:To keep a pressure-output characteristic constant without adjusting an amplification circuit, by connecting a trimming resistance in series to a bridge resistance circuit and a current supply circuit to obtain a specified pressure-output voltage characteristic with the adjustment thereof. CONSTITUTION:A resistance R5 which is connected to one end of a bridge resistance circuit RB formed on a silicone diaphragm of a pressure sensitive element 1 is allowed to be trimmed. Then, output characteristic of a semiconductor pressure sensor is adjusted with the trimming resistance R5 thus obtained. Here, the output characteristic after the manufacture of the sensor presents a straight line b0 with respect to applied pressures P0 and P1 and the output characteristic of the sensor as reference for the same pressures P0 and P1 does a straight line (a). So, the resistance value is regulated by trimming the resistance R5 to adjust current of the circuit RB so that the straight lines (a) and b0 parallel with the coincidence in variation in the voltage therebetween. Thereafter, a DC bias voltage to be applied to an input terminal 4 is adjusted to make the straight lines (a) and b0 align thereby uniforming variations in the element 1 itself.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of the Invention] The present invention relates to a diaphragm type semiconductor pressure sensor, and more particularly to a semiconductor pressure sensor whose output characteristics with respect to pressure can be made uniform.

[Summary of the Invention] A semiconductor pressure sensor according to the present invention supplies a current to a bridge-nodgy resistance circuit formed on a diaphragm of a pressure-sensitive element, obtains a voltage No. 43 from a differential amplified output at both ends, and The driving current of the resistance circuit is adjusted by a trimming resistor, and even if there are manufacturing variations in the diaphragm pressure-sensitive element itself, a constant conversion sensitivity corresponding to the pressure can be obtained.

[Prior art and its problems]

(Prior Art) As shown in FIG. 5, a conventional semiconductor pressure sensor has a pressure-sensitive element 1 formed by forming a bridge resistance circuit RB connected in a bridge shape on a silicon diaphragm, and a current supply circuit 2 consisting of an operational amplifier. A constant current is supplied to the bridge resistance circuit RB. The silicon diaphragm of the pressure sensitive element 1 is configured to be curved in response to the pressure, and resistors R1 and R are connected from both ends of the bridge resistor circuit RB.
2 to the input terminal of the operational amplifier 3 having a feedback resistor R3. Then, the resistance value of the bridge resistance circuit RB changes due to the pressure fluctuation, and the fluctuation is converted into a voltage change, amplified, and outputted to the outside.

(Problems to be Solved by the Invention) In such a conventional semiconductor pressure sensor, variations in the pressure-output sensitivity of the pressure-sensitive element 1 and the current value of the current supply circuit 2,
It is difficult to make the variation in the input offset voltage of the operational amplifier 3 constant, and in order to make the output characteristics with respect to pressure constant as a whole, the input resistances R1 and R of the operational amplifier 3 are
2 and the value of the feedback resistor R3 had to be adjusted. These resistance values must be adjusted for each individual semiconductor pressure sensor, which takes a lot of time and effort to manufacture and causes an increase in manufacturing costs. Further, when the feedback resistance and input resistance of the operational amplifier 3 are adjusted, there is a problem that the balance of the operational amplifier is lost and the effects of temperature fluctuations, common mode noise, voltage fluctuations, etc. become greater. Therefore, when one input resistance is adjusted, it is necessary to adjust the other input resistance at the same time, which poses a problem in that the adjustment takes time and effort.

[Purpose of the invention]

The present invention has been made in view of the problems of the conventional semiconductor pressure sensor, and its technical objective is to make the pressure-output characteristics constant without adjusting the amplifier circuit.

[Structure and Effect of the Invention] (Structure) The present invention provides a pressure sensitive element having a bridge resistance circuit configured on a diaphragm, a current supply circuit that supplies current to the bridge resistance circuit of the pressure sensitive element, and a bridge resistance circuit. This is a semiconductor pressure sensor that has an amplification circuit that amplifies the voltage at both ends, and as shown in FIG. The present invention is characterized in that it is configured to obtain a pressure-output voltage characteristic of .

(Function) According to the present invention having such features, current is supplied to the bridge resistor circuit configured on the silicon diaphragm of the pressure sensitive element, and the drive current is changed by the trimming resistor. In order to equalize variations in the pressure sensitive element itself, the drive current is adjusted by a trimming resistor so that the change in output becomes a predetermined value in response to a change in pressure.

(Effects) Therefore, according to the present invention, since the amplification factor of the amplifier circuit remains unchanged before and after trimming, it is possible to adjust the anger level without disturbing the balance. Furthermore, the temperature fluctuation and voltage fluctuation characteristics of semiconductor pressure sensors increase in proportion to the drive current, but in the present invention, for semiconductor pressure sensors with a large amplification factor, the drive current is adjusted to be small to reduce the output in response to pressure changes. Constant change. Therefore, the temperature characteristics and voltage characteristics can be improved compared to conventional semiconductor pressure sensors in which a predetermined output change is obtained by adjusting the amplification factor of the amplifier without reducing the drive current.

[Explanation of Examples]

FIG. 1 is a circuit diagram showing an embodiment of a semiconductor pressure sensor according to the present invention. In this figure, the same parts as in the conventional example are given the same reference numerals. Also in this embodiment, the bridge resistance circuit R formed on the silicon diaphragm of the pressure sensitive element 1
A current is supplied to B from a current supply circuit 2 consisting of an operational amplifier, and the voltage change across the bridge resistance circuit RB is controlled by a resistor R1.
, R2 between the inverting input terminal and the non-inverting input terminal of the operational amplifier 3. A feedback resistor R3 is connected between the output terminal and the inverting input terminal of the operational amplifier 3, and the input terminal 4
The configuration in which the DC bias voltage Vo is applied to the non-inverting input terminal of the operational amplifier 3 via the resistor R4 is similar to the conventional example described above.

In this embodiment, the resistor R5 connected to one end of the bridge resistor circuit RB is a resistor that can be trimmed. For example, a square plate type fixed chip resistor is used as the trimming resistor R5.
Configure to enable laser trimming.

The output characteristics of this semiconductor pressure sensor are adjusted by a trimming resistor R5. Here, as shown in FIG. 2, the applied pressure P. , Pl, the output characteristic of the semiconductor pressure sensor A is expressed as a straight line vAa, and the output characteristic of the semiconductor pressure sensor B according to this embodiment after manufacturing is a straight line. shall be shown as When adjusting the output characteristics of the semiconductor pressure sensor B to match the output characteristics of the semiconductor pressure sensor A, first trimming the trimming resistor R5 adjusts the resistance value and adjusts the current flowing through the bridge resistance circuit RB. do. That is, when the resistance value of the trimming resistor R5 is increased by trimming, the drive current of the bridge resistor circuit RB decreases, so that the amount of voltage change can be reduced. Therefore, it is a straight line with the voltage change ΔVa of bia. The drive current of the bridge resistor circuit RB is adjusted so that the voltage change Δvb of Then, as shown in Figure 3, its characteristics will be expressed by straight lines a and l.
).

Therefore, the respective changes can be made into straight lines that are equal and parallel to each other. Thereafter, by adjusting the DC bias voltage Vo applied to the input terminal 4, the straight line b2 can be made to coincide with the straight line a, as shown in FIG.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an embodiment of a semiconductor pressure sensor according to the present invention, and FIG. 2 is a change in output voltage with respect to applied pressure before adjustment of a semiconductor pressure sensor A serving as a reference and a semiconductor pressure sensor B according to this embodiment. FIG. 3 is a graph showing the output characteristics of the two semiconductor pressure sensors A and B after adjusting the resistor R5 by trimming according to this embodiment.
The figure shows two semiconductor pressure sensors A after adjusting the DC bias voltage Vo applied to the semiconductor pressure sensor B of this embodiment.
A graph showing the output characteristics of B, and FIG. 5 is a circuit diagram showing an example of a conventional semiconductor pressure sensor. 1.---1---Pressure sensing element 2----Current supply circuit 3-1 Operational amplifier 4----1 Input terminal
5-・-Output terminal R1~R4-m---Resistance
R5---Trimming resistor RB-11--
-Bridge resistance circuit patent applicant Tateishi Electric Co., Ltd. agent Patent attorney Yoshiki Okamoto (and one other person) Payroll end 3---------Actually'1t=margin R5-----)-'Nomin 7゛Kikakai RB----
7'-・7:,; This is the final blow.

Claims (1)

[Claims] (1) A pressure sensitive element having a bridge resistance circuit configured on a diaphragm, a current supply circuit that supplies current to the bridge resistance circuit of the pressure sensitive element, and an amplifier circuit that amplifies the voltage across the bridge resistance circuit. A semiconductor pressure sensor comprising: a trimming resistor connected in series with the bridge resistance circuit and the current supply circuit, and configured to obtain a predetermined pressure-output voltage characteristic by adjusting the trimming resistor. pressure sensor.