JPH10281907A - Semiconductor type stress detecting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a circuit capable of correcting the temperature characteristic of sensitivity of a pressure sensor to both positive and negative. SOLUTION: The values of both end voltages V1, V3 in a resistor R2 having a temperature characteristic are varied by the trimming regulation of a trimming resistor R3. The current It1 carried in the resistor R2 can be thus set to both positive and negative. Since the current 11 carried in a transistor TR1 is increased and decreased by the current It1, each of positive and negative temperature characteristics can be imparted to the current passing the resistor R1. The output value of an arithmetic amplifier OP1 is feedback controlled on the basis of the current carried in the resistor R1, so that each of positive and negative temperature characteristics can be imparted to the current I2 carried in a transistor TR2. Thus, the temperature characteristic of sensitivity of a pressure sensor can be corrected to both positive and negative.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor type stress detecting device utilizing a semiconductor piezoresistive effect, and is suitably applied to a pressure sensor or an acceleration sensor.

[0002]

2. Description of the Related Art A sensor chip having a gauge resistor formed thereon is fixed to a glass pedestal by anodic bonding. Different distortions are generated depending on the fixing method at this time, and the temperature characteristics of the sensor sensitivity change variously. FIG. 4 shows a circuit conventionally employed to adjust the temperature characteristics of the sensor sensitivity. In this circuit, the sensitivity of the pressure sensor is adjusted by changing the current applied to the bridge circuit. Hereinafter, the sensitivity adjustment of the pressure sensor will be described with reference to FIG.

A current is supplied to a bridge circuit composed of the gauge resistors RA, RB, RC, and RD by a current mirror circuit 200. Current mirror circuit 200
The collector of the transistor TR12 of the current mirror circuit 200 is connected to a bridge circuit, and the current I12 is supplied to the bridge circuit via the collector. Is supplied.

The collector of the transistor TR11 of the current mirror circuit 200 is connected to the collectors of the Darlington-connected transistors TR13 and TR14, and the emitter of the transistor TR14 is connected to the resistor R11 having no temperature characteristic. Also, the transistor TR1
The output terminal of the operational amplifier OP1 is connected to the base of the third amplifier. The inverting input terminal of the operational amplifier OP11 is connected to a connection point between the transistor TR13 and the resistor R11. A non-inverting input terminal is a D / A converter (not shown).
, And controls the output voltage V11 of the D / A converter to change the current I11 flowing through the resistor R11.
Change 2 The change in the current I12 changes the voltage applied to the bridge circuit to adjust the sensitivity of the bridge circuit.

However, the semiconductor type gauge resistor RA
To RD have temperature characteristics, so that the sensitivity also needs to be corrected according to the temperature characteristics of the gauge resistors RA to RD. Therefore, the temperature characteristic of the sensitivity is corrected by giving the current I12 flowing through the bridge circuit a temperature characteristic corresponding to the gauge resistances RA to RD. That is, the temperature characteristic compensation resistor R1
3 is connected in parallel to the bridge circuit, and by trimming the resistor R13, the current I12 has an arbitrary temperature characteristic to correct the temperature characteristic of the sensitivity.

[0006]

Here, consider the current flowing through the above-mentioned conventional sensitivity adjustment circuit. If the current mirror ratio is 1: n, the transistor TR1
The current flowing through 2 becomes nI11. When the combined resistance of the gauge resistances RA to RD is R12, Equations 1 and 2 are shown from the current flowing through the transistor TR12 and the current I12 flowing into the bridge circuit.

[0007]

(Equation 1)

[0008]

(Equation 2)

The above equations 1 and 2 are summarized as equation 3 below.

[0010]

(Equation 3)

The temperature characteristic of the current I12 is
Can be expressed by partially differentiating the temperature with respect to the temperature, and is expressed by Expression 4. It should be noted that only R12 changes with respect to temperature in each resistor included in Equation 4.

[0012]

(Equation 4)

As expressed by equation (4), the current I12
Becomes negative or zero. Therefore, when the temperature characteristic of the sensitivity becomes positive, the temperature dependence of the sensitivity can be eliminated based on the current I12 having the negative temperature characteristic as in the related art. In
The temperature dependency of the sensitivity cannot be eliminated based on such a current I12.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to provide a circuit capable of correcting a temperature characteristic of a semiconductor type stress detection device regardless of whether the temperature characteristic is positive or negative.

[0015]

In order to achieve the above object, the following technical means are employed. According to the first to third aspects of the present invention, the operational amplifiers (OP1, OP21)
The first circuits (TR1, TR4, TR5, TR6, TR2) that flow the first predetermined currents (I1, I21) corresponding to the outputs of
1) and detection resistors (R1, R1) provided in the first circuit.
21) means for feedback-adjusting the first predetermined current based on 21), and a second means for supplying a second predetermined current (I2, I22) proportional to the first predetermined current to the gauge resistors (RA to RB).
(TR2, TR22) and a third circuit (TR3, T3) for increasing or decreasing the first predetermined current flowing through the detection resistor based on the temperature characteristic currents (It1, It2) having temperature characteristics.
R23), and the temperature characteristic currents (It1, It2) can be adjusted by adjusting the resistance values of the trimming resistors (R3, R23).

As described above, the first predetermined currents (I1, I2) are obtained by the temperature characteristic currents (It1, It2) having the temperature characteristics.
1), the first predetermined current (I
1, I21) can have both positive and negative temperature characteristics. Then, since the feedback adjustment corresponding to the first predetermined currents (I1, I21) having the temperature characteristics is made via the operational amplifiers (OP1, OP21), the second current flowing to the gauge resistors (RA to RD) is obtained. The predetermined current (I2, I2
2) can have both positive and negative temperature characteristics.

Since the temperature characteristic currents (It1, It2) can be adjusted by adjusting the resistance values of the trimming resistors (R3, R23), the trimming resistors (R3, R2) can be adjusted.
By adjusting the resistance value of 3), it is possible to correct the temperature characteristic regardless of whether the temperature characteristic of the sensitivity of the semiconductor type stress detector is positive or negative. Specifically, the temperature characteristic resistance (R1) through which the temperature characteristic currents (It1, It2) flow due to the trimming resistances (R3, R23).
If the potential difference between the two ends can be adjusted, the temperature characteristic currents (It1, It2) can be adjusted.

[0018]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing a first embodiment of the present invention. FIG. 1 is a schematic diagram of a temperature characteristic adjusting circuit of the pressure sensor according to the present embodiment. Hereinafter, the configuration of the temperature characteristic adjusting circuit of the pressure sensor will be described with reference to FIG. As shown in FIG. 1, the circuit of the pressure sensor includes a first circuit for flowing a predetermined current corresponding to the output of the operational amplifier OP1, and a current proportional to the predetermined current and a gauge resistor RA to
The current mirror circuit 100 includes a second circuit for supplying a bridge circuit composed of RD and a third circuit for correcting a temperature characteristic of sensor sensitivity.

The bases of the transistors TR1, TR2 and TR3 in the current mirror circuit 100 are connected to each other. The collector of the transistor TR1 is connected to the Darlington-connected transistors TR4 and T4.
Connected to the collector of R5, the transistor TR4
And TR5 controls the current supply to the bridge circuit and the resistor R3.

The emitter of the transistor TR5 is connected to one end of a resistor (for detection) R1 having no temperature characteristic, and the other end of the resistor R1 is grounded. The output terminal of the operational amplifier OP1 is connected to the base of the transistor TR4. The inverting input terminal of the operational amplifier OP1 is connected to the node between the transistor TR5 and the resistor R1, and the non-inverting input terminal is connected to the output terminal of a D / A converter (not shown). Then, the current Io based on the current flowing through the resistor R1 is returned to the operational amplifier OP1, and the output of the operational amplifier OP1 is feedback-adjusted.

Further, by controlling the output voltage V1 from the output terminal of the D / A converter and changing the base current Ib of the transistor TR4, the current flowing through the resistor R1 changes. The voltage applied to the bridge circuit can be changed by the change in the current, and the sensitivity of the bridge circuit is adjusted. Note that the gauge resistor R in the bridge circuit
The midpoint potential output between A, RB, RC, and RD is amplified by an amplifier (not shown) and output as a sensor signal.

A resistor (temperature characteristic resistor) R2 having a temperature characteristic is provided between the connection point of the transistor TR5 and the resistor R1 and the transistor TR3, and a current (temperature characteristic) flowing through the resistor R2 has a temperature characteristic. Temperature characteristic current) I
The temperature characteristic of the sensor sensitivity is corrected by t1. A resistor R3 for performing trimming adjustment is connected to a connection point between the transistor TR3 and the resistor R2. The voltage V1 across the resistor R2 depends on the manner of trimming the resistor R3.
And the voltage V3 is determined, whereby the current It1 flowing through the resistor R2 can be made to act both positively and negatively with respect to the current flowing through the resistor R1.

Hereinafter, the temperature characteristic correction of the sensor sensitivity based on the trimming adjustment resistor R3 will be described based on the current flowing through the pressure sensor. First, the voltage V1 is applied from the output terminal of the D / A converter. At this time, the potential difference between the two terminals of the operational amplifier OP1 can be regarded as substantially zero. The transistors TR4 and TR5 are Darlington connected, and the base current Ib of the transistor TR4 is
Is sufficiently small, the current Ic has the same magnitude as the current Ie. Further, since the input current Io to the OP is very small and can be regarded as substantially zero, the relationship between the currents Ic and Ie is Ic ≒ Ie.

Therefore, the collector current Ic in the transistor TR1 is defined as a current I1, and the transistors TR2,
Consider currents I2 and I3 flowing in TR3. The currents I2 and I3 flowing through the transistors TR2 and TR3 are
These transistors TR2 and TR3 and the transistor TR
Since the current ratio is determined by the current mirror ratio according to the size of the transistor 1, if the size ratio of the transistors TR 1, TR 2, and TR 3 is 1: n: m, the currents I 2 and I 3 Are I2 = nI1 and I3 = mI1, respectively.

FIG. 2 is an equivalent circuit diagram of the current mirror circuit 100 for correcting the temperature characteristics of the sensor sensitivity. At this time, as described above, since the current I3 flowing through the transistor TR3 is represented by I3 = mI1, Equations 5 and 6 are derived.

[0026]

(Equation 5)

[0027]

(Equation 6)

In addition, the above Expressions 5 and 6 can be summarized as Expression 7.

[0029]

(Equation 7)

The temperature characteristic of the current I3 can be expressed by partially differentiating the current I3 with respect to the temperature, and is expressed by Expression 8. It should be noted that only R2 changes with respect to the temperature in each resistor included in Expression 8.

[0031]

(Equation 8)

As shown in Equation 8, the temperature characteristic of the current I3 is positive or negative depending on the magnitude of m and R1 / R3. Table 1 shows the temperature characteristics of I3 and the relationship between V1 and V3 based on the relationship between m, R1, and R3.

[0033]

[Table 1] As shown in the above table, by changing the resistance values of the resistors R1 and R3 in the vicinity of m ≒ R1 / R3, V1
And V3 can be set. That is, in the pressure sensor circuit shown in FIG. 1, the magnitude relationship between V1 and V3 can be set by trimming and adjusting the resistance value of the resistor R3. That is, the current I flowing through the resistor R2
The current I1 is increased or decreased by t1, and the current flowing through the resistor R1 can have temperature characteristics in either positive or negative polarity. Since the feedback control of the operational amplifier OP1 is performed based on the current flowing through the resistor R1, the temperature characteristic can be set to either positive or negative for the current I2.

Therefore, regardless of whether the temperature characteristic of the sensitivity that varies due to the method of fixing the sensor chip of the pressure sensor to the glass pedestal is positive or negative, it is possible to correct the temperature characteristic of the sensitivity by adjusting the trimming of the resistor R3. it can. In this case, the resistor R3 for trimming adjustment may be formed in a range where R3 ≒ R1 / m. (Second Embodiment) FIG. 3 is a schematic circuit diagram of a pressure sensor according to a second embodiment to which the present invention is applied.

In the first embodiment, a PNP type current mirror circuit is used, but in this embodiment, an NPN type current mirror circuit is used. Also,
This embodiment does not employ the Darlington connection. As shown in FIG. 2, the transistors TR21, TR22, T
R23 are all NPN-type transistors, and the amount of current flowing through each of the transistors TR21, TR22, TR23 is adjusted by an applied voltage V21 of a D / A converter (not shown).

The resistors R21 and R23 do not have temperature characteristics, and the resistor R22 has temperature characteristics. Among them, the resistor 23 is a resistor used for trimming adjustment. Assuming that the current mirror ratio is 1: n: m as in the first embodiment, the magnitudes of the currents I22 and I23 are I22 = nI21 and I23 = mI2, respectively.
It becomes 1. Since the resistors R21, R22, and R23 play the same role as the resistors R1, R2, and R3 in the first embodiment, the relational expressions derived from the currents flowing through the resistors R21, R22, and R23 are as follows. It will be the same.

Therefore, the temperature characteristics of the current It2 flowing through the resistor R22 can be made to have either positive or negative polarity with respect to the current I21 based on the trimming adjustment of the resistor R23. Both positive and negative polarities can be set. Thereby, the temperature characteristic of the sensor sensitivity can be corrected.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a circuit for adjusting a temperature characteristic of a pressure sensor according to an embodiment of the present invention.

FIG. 2 is an equivalent circuit diagram of a current mirror circuit of a correction part of a temperature characteristic of sensitivity in the pressure sensor shown in FIG.

FIG. 3 is a schematic diagram of a circuit for adjusting a temperature characteristic of a pressure sensor according to a second embodiment.

FIG. 4 is a schematic diagram of a circuit for adjusting a temperature characteristic of a conventional pressure sensor.

[Explanation of symbols]

TR1 to 6: transistor, OP11: operational amplifier, R
1, R3: resistance without temperature characteristics, R2: resistance with temperature characteristics, RA, RB, RC, RD: gauge resistance.

Claims (3)

[Claims] A gauge resistor (RA to R) which changes its resistance value based on a stress displacement of a thin portion provided on a semiconductor substrate.
D), wherein the semiconductor type stress detecting device detects stress based on a change in the resistance value of the gauge resistor. 1 circuit (TR1,
TR4, TR5, TR6, TR21); a detection resistor (R1, R21) provided in the first circuit for detecting the first predetermined current; and the first current based on the detection current of the detection resistor. Means for feedback-adjusting the predetermined current, and a second resistance proportional to the first predetermined current is added to the gauge resistance.
Circuit (TR) for flowing the predetermined currents (I2, I22)
2, TR22), and a third circuit (TR3) for flowing a temperature characteristic current (It1, It2) having a temperature characteristic and for increasing or decreasing the first predetermined current flowing to the detection resistor based on the temperature characteristic current. ,
TR23), wherein the third circuit has a trimming resistor (R3, R23), and the temperature characteristic current can be adjusted by adjusting the resistance value of the trimming resistor. Semiconductor stress detector. 2. The semiconductor type stress detecting device according to claim 1, wherein said first circuit, second circuit and third circuit are constituted by a current mirror circuit. 3. The temperature characteristic current flows through temperature characteristic resistances (R2, R22) having a temperature characteristic connecting the first circuit and the third circuit, and the resistance value of the trimming resistance. The semiconductor type stress detecting device according to claim 1, wherein the adjustment is such that a potential difference at both ends of the temperature characteristic resistor can be adjusted.