JPS62267604A - Temperature compensating circuit for semiconductor transducer - Google Patents

Abstract

PURPOSE:To obtain a temperature compensating circuit suitable for MOS integration, by connecting in common the collectors and bases of a pair of bipolar transistors, respectively, and connecting them to a source voltage supply terminal and an output terminal of an operation amplifier. CONSTITUTION:A collector and a base of a pair of bipolar transistors 21, 22 and connected in common, respectively, and led to a power supply voltage supply terminal 23 and an output terminal 24 of an operational amplifier 20. Also, a temperature coefficient setting circuit 200 and a bridge circuit 100 containing a detecting element are provided. In this way, a vertical bipolar transistor in which an n-type semiconductor substrate 34 for forming a CMOS integrated circuit is a collector, a p-well area 35 is a base, and an n<+> area 36 for forming a source.drain area of an n-channel transistor is an emitter can be realized by a usual CMOS manufacturing process.

Description

[Detailed description of the invention]

[Industrial Field of Application] [Prior Art] Pressure transducers using semiconductor piezoresistive elements are well known as semiconductor transducers. The cage factor of the piezoresistive element generally exhibits a negative temperature coefficient, and the pressure-to-electricity conversion sensitivity of a converter made of a bridge circuit including the piezoresistive element decreases as the ambient temperature rises. Conventionally, a temperature compensation circuit at an integrated level that compensates for this decrease in sensitivity utilizes the negative temperature coefficient of the base-emitter forward pressure vBE of a bipolar transistor to convert a voltage proportional to VBI from the power supply voltage. A temperature compensation circuit (IEICE Technical Report ED80-20) in which the bridge excitation voltage is increased linearly with respect to warm temperature rise by subtraction. (2) The base-emitter lightning pressure difference ΔvBε of bipolar transistors with different MR densities is proportional to the absolute temperature (IEEJ Journal of Solid State Circuits (IEEJ, 5)
solid-8tate C1rcuits) 6 volumes,
1971, pp. 2-7), we developed a temperature compensation circuit (Sensors and Acti, z-ta) that gave a positive temperature coefficient to the bridge excitation voltage.
ra and Actuators) Volume 4, 1983
2013, pp. 63-69). 2 above
Both examples use bipolar integration technology. However, the goal of integrated converters is to make them multifunctional and intelligent. Integrated circuit technology and

[Well, MO8 technology is superior to bipolar technology. That is, future integrated converters will include semiconductor sensing elements and P+-
The board is equipped with not only a temperature compensation function, but also an amplification function, a multiplex function, an arithmetic processing function within the chip, an A/Df conversion function that enables a digital interface with a computer, a digital signal processing function, etc. This is required. These requirements include switched output circuits, analog switches, and A/D conversion microcontrollers.
MO8 integrated circuit technology, which has a proven track record in the field of analog-digital mixed circuits including processors, is more suitable than bipolar technology because it has lower consumption, more power, and can be integrated on a larger scale. However, the circuit configurations of known integrated temperature compensation circuits are all based on bipolar integration, and are fundamentally incompatible with the MO8 integration process. In order to solve the above-mentioned problems, a temperature compensation circuit (Japanese Patent Application No. 187633/1982) was devised which has a width suitable for MO8 integration. FIG. 4 shows the configuration of this temperature control circuit. In the figure, 100 is a piezoresistive element 1. 2. 3
．． 4 is a bridge circuit, 5 is a reference voltage generation circuit,
6 is an amplifier, 7 is a resistor, and 8 is a temperature-sensitive diffused resistor having a larger positive IA coefficient than resistor 7. In this circuit, the resistor 7 and the temperature-sensitive diffused resistor 8 form a negative feedback loop that returns part of the normal pressure output from the operational amplifier 6 to the inverting input terminal. As a circuit including the operational amplifier 6,
The output voltage of the reference voltage generation circuit 5 is an inverting circuit, and the output voltage of the operational amplifier 6 is used as the bridge circuit 1.
00 is excited. According to such a circuit configuration, a positive temperature gradient based on the temperature coefficient of the temperature-sensitive diffused resistor 8 can be given to the excitation voltage of the bridge circuit 100, so that a bridge circuit based on the negative temperature coefficient of the piezoresistance coefficient can be applied. The negative temperature coefficient of the 100 piezoelectric conversion sensor KO can be compensated for by the positive temperature coefficient of the temperature-sensitive diffused resistor 8. The reference voltage generating circuit 5 used in the circuit of FIG.
Hanging type MO8FET and Debris type MO8
Circuit method for detecting the difference in threshold voltage of FET (
IEEJ Journal of Solid State Research (IEEJ, 5
solid-8tate C1rcuits) Volume 13, 1
978, pp. 767-774) by using the ~108 integration process, and this and M
A MOS-integrated temperature compensation circuit is constructed by integrating an O8 operational amplifier, a temperature-sensitive diffused resistor, and a diffused piezoresistive element on the same semiconductor substrate. [Problem 1 to be Solved by the Invention Above, a conventional example of a temperature compensation circuit suitable for MO8 integration has been described. However, the circuit of FIG. 4 has the disadvantage that sensitivity compensation over a wide temperature range is difficult because the temperature-sensitive diffused resistor 8 includes a high-order term (mainly a quadratic term) of the temperature coefficient. Furthermore, all sensitivity compensation circuits that do not use temperature-sensitive diffused resistors are based on a bipolar manufacturing process, and it has been impossible to realize the circuit configuration using the MO8 manufacturing process. As described above, there is no conventional temperature compensation circuit for semiconductor converters that can achieve sensitivity temperature compensation over a wide temperature range and is suitable for MO8 integration. There are many things. [Means for solving the problem] The structure of the temperature compensation circuit of the semiconductor converter of the present invention includes a pair of bipolar transistors whose respective collectors and bases are connected in common, and a voltage between the base and emitter of this transistor pair. A temperature coefficient setting circuit consisting of a resistor network and an operational amplifier that sets the temperature coefficient of the output voltage based on the difference, and a bridge circuit driven by the output voltage of the temperature coefficient setting circuit and including a sensing element on at least one side. It is characterized by: The temperature compensation circuit of the semiconductor converter of the present invention can also be configured such that the output of the temperature coefficient setting circuit is amplified and supplied to the bridge circuit. [Example] Hereinafter, the present invention will be explained in detail with reference to Examples. FIG. 1 is a schematic diagram showing one embodiment of the present invention. In the figure, 100 is a bridge circuit consisting of piezoresistive elements 1, 2, 3.4 as shown in FIG. .33 and an operational amplifier 20, the bridge circuit 100 is excited by the output voltage of the operational amplifier circuit 20. Bipolar transistor pair 21.22 in this example
The collector and base of are connected in common and led to the power supply voltage supply terminal 23 and the output terminal 24 of the operational amplifier 20, and the emitters are connected to a resistor 33 and a resistor 3, respectively.
1.32 to the ground terminal. On the other hand, the inverting input terminal 25 of the operational amplifier 20 is connected to the emitter of the transistor 21, and the non-inverting input terminal 26 is connected to the midpoint between the resistors 31 and 32, which are connected to the emitter of the bipolar transistor 22. Next, the temperature characteristics of the bridge excitation voltage Vexc supplied by the temperature coefficient setting circuit 200 in this embodiment will be explained. In the circuit of FIG. 1, the base-emitter voltages of transistors 21 and 22 are set to Vbe1 and Vbe□.
, the collector current is 11 and the resistor is 2, and the resistance is 31.32.
Let the resistance values of 33 be 1°R2 and R3. At this time,
Since the inverting input terminal 25 of the operational amplifier 20 has the same potential as the non-inverting input terminal 26 due to a 'virtual short circuit', the bridge excitation voltage Vexc obtained at the output terminal 24 of the operational amplifier circuit is as follows. .VeXC=Vbel+I 1・R3=Vbe1+I
21 a. Here, the following equation is obtained. In the above equation, JVbe is expressed as the difference between Vbe1 and Vbe2: Boltzmann constant T: Absolute temperature q: Electron charge IJ: Saturation current of transistor 21 I°) Saturation current of transistor 22 S2 ・ Since JVbe is expressed as follows: Expressed by the formula. In the above equation, the first term on the right side is the base-emitter voltage V
be 1 is 0.5 to 0.7 V at room temperature, -2,0
It has a negative temperature coefficient of about mV/'C. Furthermore, the second term on the right side is proportional to the absolute temperature, and its proportionality constant (K/Q) ・(Rz/R1)pnc (R2
/R3) (IS2/Ist) ]. Therefore, the circuit constants (R2/R1), (Rz/R
i) and Is2/Is1, it is possible to give the bridge drive voltage Vexc a desired positive temperature coefficient necessary for sensitivity temperature compensation. A major feature of the circuit configuration of this embodiment is that the collectors of bipolar transistors 21 and 22 are commonly connected to a power supply 1' voltage supply terminal 23. Conventional temperature compensation circuits using bipolar transistors are not configured so that the collector is connected to a common terminal such as a power supply voltage supply terminal or a ground terminal, and such a transistor is realized using the MO8 manufacturing process. On the other hand, the transistor 2 used in this embodiment
1 and 22 may have a common collector, so as shown in the cross-sectional view of FIG. A vertical bipolar transistor having the n+ region 36 for forming the source and drain regions as an emitter can be realized by a conventional CMO8 manufacturing process. The base-emitter voltage Vb used in this example is still
Since both the temperature coefficients of the difference ΔVbe between e and Vbe do not include high-order terms, it is possible to perform g-degree temperature compensation over a wider temperature range than in the temperature compensation circuit of FIG. 4 using a temperature-sensitive diffused resistor. Therefore, according to the first embodiment, an excellent temperature compensation circuit for a semiconductor converter is realized which can achieve temperature compensation over a wide temperature range and is suitable for MOS integration. In the above embodiment, the base-emitter voltage of the transistor 21, the voltage Vbe1, and the voltage drop of the resistor 33, 1·R, (=
The output voltage of the operational amplifier 20 that calculates the sum of I, 1t2) is taken as the bridge drive voltage Vexc.
Amplify the output ♂′ pressure (current, ) to obtain the bridge drive voltage V
Setting it as exc is useful for increasing the sensitivity and stabilizing the semiconductor converter. An example of such a temperature compensation circuit is shown in FIG. FIG. 3 rt is a diagram showing a second modified embodiment of the present invention, in which the bridge circuit 100 and the temperature coefficient setting circuit 200 have the same configuration as in FIG. 1, but an operational amplifier 40 is added to these I'Pi1.
A bridge drive circuit 300 consisting of resistors 41 and 42 is added. The bridge drive circuit 30
0, the non-inverting input quadruple 46 of the operational amplifier 4o is connected to the output of the temperature coefficient setting circuit 200, and a resistor 41 is connected between the inverting input terminal 45 of the amplifier 4o and the ground terminal.
A resistor 42 is connected between the inverting input terminal 45 and the output terminal 44, respectively. The bridge circuit 100 is configured to be excited by the output voltage of the operational amplifier 4o. In this embodiment, the resistor 41 and the resistor 42 are connected to the operational amplifier 4.
A so-called negative feedback loop is formed in which a part of the output voltage of 0 is returned to the inverting input terminal, and the circuit including the operational amplifier 40 is a non-inverting amplifier circuit for the output voltage of the temperature coefficient setting circuit 200. It consists of Therefore, assuming that the resistance values of the resistor 41 and the resistor 42 are R11 and R12, the output voltage of the operational amplifier 4o, that is, the excitation voltage Vexc supplied to the bridge circuit 00 is expressed by the following equation. RR2kT R2l5 vexC=(]10wK)・(Vbe1+πd・]”en
π1r11) As is clear from the above equation, according to this embodiment, as in the first embodiment, the temperature coefficient setting circuit 200
(R2/R1), (R2/R3) and Is2/I
By setting s1, the temperature coefficient in the second term on the right side can be set to a desired value, and the magnitude of the excitation voltage Vexc can be set to a desired value by setting the resistance ratio (R12/all) between the resistor 42 and the resistor 41 of the bridge drive circuit 300. Therefore, an excellent temperature compensation circuit for a semiconductor converter can be obtained that can simultaneously achieve temperature compensation of sensitivity and sensitivity adjustment. In the above embodiment, the bridge drive circuit 300 is a non-inverting amplifier circuit using the operational amplifier 40, but this is just an example, and the bridge drive circuit includes an inverting amplifier circuit, a differential amplifier circuit, a voltage follower circuit, etc. , various circuit configurations using operational amplifiers can be used. In addition, in the above two embodiments, the piezoresistive element is mainly of the Kp type and the bipolar transistor is of the n-p-n type because the n-type semiconductor substrate (p-well 0MO8 manufacturing process) is used. Even when an n-type semiconductor substrate (n-well CMO8 manufacturing process) is used, p-n
A similar circuit can be realized using -p-type bipolar transistors. The above is the case for pressure transducers using piezoresistive elements. However, the present invention is widely applicable not only to pressure transducers but also to temperature compensation circuits for semiconductor transducers that use semiconductor sensing elements that exhibit a change in resistance vL in response to changes in a sensing target. [Effects of the Invention] As described above, according to the present invention, all the drawbacks of the above-mentioned prior art are eliminated, and an extremely useful temperature compensation circuit suitable for MO8 integration is realized. The temperature compensation circuit according to the present invention contributes to making a semiconductor converter intelligent by combining it with a microcomputer, and its effects are significant.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing one embodiment of the present invention, FIG. 2 is a schematic cross-sectional view showing an example of the structure of a bipolar transistor which is a component of this embodiment, and FIG. 3 is a second embodiment of the present invention. FIG. 4 is a circuit diagram of a conventional example of a temperature compensation circuit for a semiconductor converter. 1 to 4...Piezoresistance element, 5...Group/base st
Pressure generation circuit, 6.20.40... operational amplifier,
7゜3], 32.33, 41.42...Resistance,
8... Temperature-sensitive diffusion resistance, 21.22...
Bipolar transistor, 23... Voltage supply terminal, 24.44. Old... Output terminal, 25.45.46.
・River/reverse/reverse input terminal, 26...Non-inverting input terminal, 34...N-type semiconductor substrate, 35...
・p-well region, 36...n+ region 100
...Bridge circuit, 200 ... Temperature coefficient setting circuit, 300 ... Bridge drive circuit. Half a time ￥-2ㅅv3 current ￥4-times

Claims (1)

[Claims] 1) A resistor circuit comprising a bipolar transistor pair in which each collector and each base are connected in common, and a humidity coefficient of the output voltage is set based on the difference in voltage between the base of this transistor pair and each emitter. 1. A temperature compensation circuit for a semiconductor converter, comprising: a temperature coefficient setting circuit comprising a network and an operational amplifier; and a bridge circuit driven by the output voltage of the temperature coefficient setting circuit and including a sensing element on at least one side. 2) A temperature compensation circuit for a semiconductor converter according to claim 1, wherein the output of the temperature coefficient setting circuit is amplified and supplied to the bridge circuit.