Sensor drive circuit

Abstract

The present application provides a sensor driving circuit which can correct output error of a temperature-based sensor with high precision through a simple circuit structure. The sensor driving circuit drives a sensor whose temperature characteristic of a first order coefficient is negative and whose temperature characteristic of a second order coefficient is positive by a current, and includes: a first current source which generates a first current whose temperature characteristic of a first order coefficient is positive and whose temperature characteristic of a second order coefficient is negative; a second current source which generates a second current whose temperature characteristic of a first order coefficient is negative and whose temperature characteristic of a second order coefficient is negative; a first current operation section which adds the first current and the second current to generate a third current; a current amplification section which amplifies the third current to generate an amplified current; a constant current source which generates a constant current after temperature correction; and a second current operation section which adds the constant current to the amplified current to generate a driving current for driving the sensor.

Description

Technical Field

[0001] This invention relates to a sensor driving circuit. Background Technology

[0002] A technique has been developed that improves the temperature characteristics of the sensor's span voltage by giving the sensor's drive current or drive voltage temperature characteristics.

[0003] For example, the following technology is disclosed in Patent Documents 1 and 2: when generating a drive current, the primary component of the temperature characteristics of the sensor can be compensated by dividing the power supply voltage through a temperature-sensing resistor (a thermistor or a group of resistors with different temperature characteristic coefficients).

[0004] Furthermore, Patent Document 3 discloses a technique in which a temperature-sensing resistor is added to the gain when generating the driving voltage of the sensor from the BGR (Band Gap Reference) voltage, thereby compensating for the secondary component of the sensor's temperature characteristics.

[0005] Furthermore, Patent Document 4 discloses a technique in which the current is increased or decreased based on the output of a temperature sensor, thereby compensating for the temperature characteristics of the temperature sensor.

[0006] However, none of the technologies in Patent Documents 1-4 can compensate for the second component of the temperature characteristic of the sensor's span voltage using a relatively simple circuit structure. Therefore, none of the technologies in Patent Documents 1-4 can accurately correct the output error of a temperature-based sensor using a relatively simple circuit structure.

[0007] Furthermore, when correcting sensor output errors based on high-precision temperature, digital correction methods are considered. Digital correction involves acquiring temperature data, pre-storing the corresponding correction value (function) in a storage area (such as NVM, non-volatile memory), and then correcting the sensor's output error after digitization via A / D conversion using an arithmetic unit. For example, in a structure with only one A / D converter relative to the temperature sensor used for acquiring the temperature and the sensor to be corrected, a multiplexer is needed to switch between the outputs of the sensor to be corrected and the temperature sensor, and then perform A / D conversion on each output. In this case, compared to not performing this switching operation, the temperature acquisition switching operation typically incurs several milliseconds of extra time. Using multiple A / D converters can eliminate this extra time, but this increases the chip area, affecting the unit price of the sensor driver circuit, which is not a desirable approach.

[0008] Patent Document 1: Japanese Patent Application Publication No. 2001-091296

[0009] Patent Document 2: Japanese Patent Application Publication No. 09-101211

[0010] Patent Document 3: Japanese Patent Application Publication No. 2001-091387

[0011] Patent Document 4: Japanese Patent Application Publication No. 11-108786 Summary of the Invention

[0012] One embodiment of the sensor driving circuit is a sensor driving circuit that drives a sensor whose temperature characteristic of current has a negative first coefficient and a positive second coefficient. It comprises: a first current source that generates a first current with a positive first coefficient and a negative second coefficient for its temperature characteristic; a second current source that generates a second current with a negative first coefficient and a negative second coefficient for its temperature characteristic; a first current calculation unit that adds the first current and the second current to generate a third current; a current amplification unit that amplifies the third current to generate an amplified current; a constant current source that generates a constant current after temperature correction; and a second current calculation unit that adds the constant current to the amplified current to generate a driving current for driving the sensor.

[0013] According to one embodiment of the sensor driving circuit, the output error of a temperature-based sensor can be corrected with high precision using a relatively simple circuit structure. Furthermore, according to another embodiment of the sensor driving circuit, the output error of the temperature-based sensor is corrected at the point in time when it has already been input to the AD converter using an analog method. Therefore, it is not necessary to switch the AD converter to obtain the temperature, and thus no time is generated for obtaining the temperature. Attached Figure Description

[0014] Figure 1 The circuit structure of the sensor driving circuit in the first embodiment is shown.

[0015] Figure 2 This is an example of the correction result for the temperature characteristics of the span voltage of a MEMS pressure sensor based on the sensor driving circuit of the first embodiment.

[0016] Figure 3 The circuit structure of the sensor driving circuit in the second embodiment is shown.

[0017] Figure 4 The circuit structure of the sensor driving circuit in the third embodiment is shown.

[0018] Figure 5 The circuit structure of the sensor driving circuit in the fourth embodiment is shown. Detailed Implementation

[0019] Hereinafter, one embodiment will be described with reference to the accompanying drawings.

[0020] (First Implementation)

[0021] Figure 1 The circuit structure of the sensor driving circuit 100 according to the first embodiment is shown. Figure 1 The sensor driving circuit 100 shown can current-drive the MEMS pressure sensor 12. Specifically, the sensor driving circuit 100 causes the driving current *lout* of the MEMS pressure sensor 12 to have a temperature characteristic (including a quadratic component) opposite to the temperature characteristic of the span voltage of the MEMS pressure sensor 12, thereby eliminating the quadratic component of the temperature characteristic of the span voltage of the MEMS pressure sensor 12. Therefore, the sensor driving circuit 100 can accurately correct the output error of the temperature-based MEMS pressure sensor 12. Figure 1 In the example shown, the detection signal (analog signal) of the MEMS pressure sensor 12 is provided to the AD converter 14, which converts it into a digital signal.

[0022] like Figure 1As shown, the MEMS pressure sensor 12 is a bridge circuit composed of four piezoelectric resistor elements 12a to 12d. The sensor driving circuit 100 of the first embodiment is not limited to driving the MEMS pressure sensor 12, but can also be used to drive other sensors (e.g., force sensors, semiconductor strain gauges, accelerometers, gyroscopes, etc.).

[0023] like Figure 1 As shown, the sensor driving circuit 100 includes: a first current source 110, a second current source 120, a connection point A, a current amplification unit 130, a first constant current source 140, a connection point B, and a fine-tuning block 150.

[0024] The first current source 110 generates a first current I1 with a positive first-order coefficient and a negative second-order coefficient in its temperature characteristic. Specifically, the first current source 110 generates the first current I1 through I1 = V1 / R1. Both the voltage V1 and the resistance R1 have positive temperature characteristics. Figure 1 In the example shown, the first current source 110 is configured to include a bipolar transistor 111 and an NMOSFET 112 (an example of a "first resistor"). Furthermore, in Figure 1 In the example shown, the first current source 110 uses the voltage (Vref - Vf1) obtained by subtracting the threshold voltage Vf1 of the bipolar transistor 111 from a constant voltage (i.e., a constant voltage with flat temperature characteristics) Vref derived from the bandgap reference voltage (PTAT voltage). Additionally, the first current source 110 uses an NMOSFET 112 in its on-state as resistor R1. Furthermore, in... Figure 1 In the example shown, the first current source 110 applies the voltage (Vref - Vf1) to the drain terminal of the NMOSFET 112, thereby generating the first current I1.

[0025] The second current source 120 generates a second current I2 with negative first-order and negative second-order coefficients in its temperature characteristics. Specifically, the second current source 120 generates the second current I2 through I2 = V2 / R2. Both the voltage V2 and the resistance R2 have negative temperature characteristics. Figure 1 In the example shown, the second current source 120 is configured to include a bipolar transistor 121 and a polysilicon resistor 122 (an example of a "second resistor"). Furthermore, in Figure 1 In the example shown, the second current source 120 uses the threshold voltage Vf2 of the bipolar transistor 121 as the voltage V2. Additionally, the second current source 120 uses a polysilicon resistor 122 as the resistor R2. Furthermore, in... Figure 1In the example shown, the second current source 120 generates the second current I2 by applying the threshold voltage Vf2 to the polysilicon resistor 122.

[0026] Connection point A is an example of a "first current calculation unit". Connection point A connects the first current source 110 and the second current source 120. Thus, connection point A adds the first current I1 generated by the first current source 110 and the second current I2 generated by the second current source 120 to generate the third current ITC.

[0027] By adding the first-order coefficient (positive) of the temperature characteristic of the first current I1 to the first-order coefficient (negative) of the temperature characteristic of the second current I2, the third current ITC generated at connection point A has a relatively small (near 0) first-order coefficient. Furthermore, by making the contribution of the temperature characteristics of the first current I1 and the second current I2 consistent, the first-order coefficient of the third current ITC can be made to be 0 or near 0. For example, in an environment where the room temperature is set to 20–30°C, preferably 22–28°C, and more preferably 23–27°C, the current values ​​of the first current I1 and the second current I2 can be set, for example, to I1 / I2 = 0.7–1.3, preferably I1 / I2 = 0.8–1.2, and more preferably I1 / I2 = 0.9–1.1.

[0028] In addition, by adding the negative quadratic coefficient of the temperature characteristic in the first current I1 to the negative quadratic coefficient of the temperature characteristic in the second current I2, the third current ITC generated at the connection point A has a relatively large negative quadratic coefficient.

[0029] It is preferable to pre-adjust the resistance R2 of the polysilicon resistor 122 so that the ratio of the primary coefficient to the secondary coefficient in the temperature characteristic of the third current ITC becomes equal to or approximately the ratio of the primary coefficient to the secondary coefficient in the opposite characteristic of the temperature characteristic of the span voltage.

[0030] The current amplification unit 130 amplifies the third current ITC generated at connection point A by a factor of m, generating the amplified current ITC'. Figure 1 In the example shown, the current amplification unit 130 is composed of a current mirror circuit. Here, it is preferable that the current amplification unit 130 amplifies the third current ITC by a factor of m, such that the magnitude of the quadratic coefficient of the temperature characteristic in the amplified current ITC' becomes equal to or approximately the magnitude of the quadratic coefficient of the temperature characteristic opposite to the temperature characteristic of the span voltage of the MEMS pressure sensor 12.

[0031] The first constant current source 140 generates a temperature-corrected first constant current Ic (i.e., a constant current with flat temperature characteristics). Furthermore, it is preferable to appropriately adjust the first constant current Ic based on the resistance value of the MEMS pressure sensor 12, the supplied power supply voltage VDD, etc., so that the drive current Iout becomes a predetermined value (e.g., 300uA) at a predetermined reference temperature (e.g., 25°C).

[0032] Connection point B is an example of a "second current calculation unit". Connection point B connects the current amplification unit 130 to the first constant current source 140. Thus, connection point B adds the amplified current ITC' generated by the current amplification unit 130 to the first constant current Ic generated by the first constant current source 140 to generate the drive current Iout for driving the MEMS pressure sensor 12.

[0033] The fine-tuning block 150 is an example of a "fine-tuning section". The fine-tuning block 150 is capable of fine-tuning (adjusting) various parts of the sensor drive circuit 100. For example, the fine-tuning block 150 can fine-tune the resistance R2 of the polysilicon resistor 122 in the second current source 120, the resistance value of the variable resistor that determines the constant voltage Vref in the first current source 110, the amplification rate m of the current amplification section 130, etc. Regarding the fine-tuning of the fine-tuning block 150, digital fine-tuning is envisioned, but laser fine-tuning is also possible.

[0034] According to the above-described structure, the sensor driving circuit 100 of the first embodiment can generate a driving current Iout having a temperature characteristic (including a secondary characteristic) that is opposite to the temperature characteristic of the span voltage of the MEMS pressure sensor 120, and drive the MEMS pressure sensor 120 through this driving current Iout. Therefore, the sensor driving circuit 100 of the first embodiment can eliminate the secondary component of the temperature characteristic of the span voltage of the MEMS pressure sensor 120 during the analog signal processing stage. As a result, the output voltage Vout of the MEMS pressure sensor 120 is Vout≈1 / 2×π44×σ×R×Iout (where π44 is the piezoelectric resistance coefficient, σ is the stress applied to the element), and π44×R is a characteristic opposite to Iout, thus resulting in a flat temperature characteristic. Therefore, according to the sensor driving circuit 100 of the first embodiment, the output error of the temperature-based MEMS pressure sensor 120 can be corrected with high precision using a relatively simple circuit structure.

[0035] (Example)

[0036] Next, refer to Figure 2 An embodiment of the sensor driving circuit 100 of the first embodiment will be described. Figure 2 This is an example of the correction result of the temperature characteristics of the span voltage of the MEMS pressure sensor 12 based on the sensor drive circuit 100 of the first embodiment.

[0037] In this embodiment, the span voltage of the MEMS pressure sensor 12 when 4 kPa and 300 uA are applied is measured as the measured data, and a temperature characteristic opposite to that of the measured data is derived. Furthermore, in this embodiment, the following simulation is performed: the MEMS pressure sensor 12 is driven using a drive current with the derived opposite temperature characteristic as the drive current Iout generated by the sensor drive circuit 100 of the first embodiment.

[0038] In addition, the conditions used in this embodiment are as follows.

[0039] • Power supply voltage: 3.3V

[0040] • The voltage V1 of the first current source 110 uses a constant voltage of 1.1V.

[0041] • Dimensions of the NMOSFET112 of the first current source 110: W = 2µm, L = 35µm

[0042] The resistance value R2 of the polysilicon resistor 122 is 86kΩ.

[0043] • At the reference temperature of “25℃”, the first constant current Ic output from the first constant current source 140 was adjusted so that the drive current Iout became “300uA”.

[0044] exist Figure 2 In the diagram, dashed lines represent the temperature characteristics of the span voltage before correction, and solid lines represent the temperature characteristics of the span voltage after correction. Figure 2 In this context, the span voltage at the reference temperature of "25°C" is depicted as 100%.

[0045] like Figure 2 As shown, in the temperature characteristics of the span voltage before correction, the span voltage varies significantly within the temperature range of 0–50°C. On the other hand, as… Figure 2 As shown, in the temperature characteristics of the corrected span voltage, it was confirmed that the variation of the span voltage is relatively small within the temperature range of 0 to 50°C.

[0046] Specifically, in the temperature characteristics of the span voltage before correction, the span voltage variation was 1.6%. In contrast, it was confirmed that in the temperature characteristics of the corrected span voltage, the span voltage variation could be converged within the target range of ±0.1%, and the span voltage variation could be made very small, at 0.02%.

[0047] (Second Implementation)

[0048] Next, refer to Figure 3 The second embodiment will be described. Figure 3 The circuit structure of the sensor driving circuit 100-2 according to the second embodiment is shown. Hereinafter, the changes of the sensor driving circuit 100-2 according to the second embodiment compared with the sensor driving circuit 100 of the first embodiment will be described.

[0049] Figure 3 The sensor driving circuit 100-2 shown does not have a connection point B. Instead, the sensor driving circuit 100-2 has a connection point C between connection point A and the current amplification section 130, and the first constant current source 140 is connected to this connection point C. That is, Figure 1 The sensor drive circuit 100 shown has a first constant current source 140 after the current amplification section 130. In contrast, Figure 3 The sensor drive circuit 100-2 shown has a first constant current source 140 set in front of the current amplification section 130, which is different from the other two.

[0050] Connection point C is an example of a "second current calculation unit". Connection point C connects connection point A to the first constant current source 140. As a result, connection point C subtracts the first constant current Ic generated by the first constant current source 140 from the third current ITC generated by connection point A to generate a fourth current ITC2.

[0051] exist Figure 3 In the sensor driving circuit 100-2 shown, the current amplification unit 130 amplifies the fourth current ITC2 generated at connection point C by a factor of m, generating a driving current Iout2 for driving the MEMS pressure sensor 12. Preferably, the current amplification unit 130 amplifies the fourth current ITC2 by a factor of m, such that the magnitude of the quadratic coefficient of the temperature characteristic in the driving current Iout2 is equal to or approximately the magnitude of the quadratic coefficient of the temperature characteristic opposite to the temperature characteristic of the span voltage of the MEMS pressure sensor 12.

[0052] The sensor driving circuit 100-2 of the second embodiment, through the above-described structure, can adjust the third current ITC (subtracting the first constant current Ic) by the first constant current Ic generated by the first constant current source 140 before the current amplification unit 130 performs amplification processing, thereby generating a fourth current ITC2. Furthermore, the sensor driving circuit 100-2 of the second embodiment can amplify the fourth current ITC2 to m times using the current amplification unit 130, generating a driving current Iout2 with a temperature characteristic (including a quadratic characteristic) opposite to the temperature characteristic of the span voltage of the MEMS pressure sensor 12, and drive the MEMS pressure sensor 12 through this driving current Iout2. Thus, the sensor driving circuit 100-2 of the second embodiment can eliminate the quadratic component of the temperature characteristic of the span voltage of the MEMS pressure sensor 12 during the analog signal processing stage. As a result, the output voltage Vout of the MEMS pressure sensor 12 is Vout≈1 / 2×π44×σ×R×Iout, where π44×R is a characteristic opposite to Iout, thus flattening the temperature characteristic. Therefore, according to the sensor driving circuit 100-2 of the second embodiment, the output error of the temperature-based MEMS pressure sensor 12 can be corrected with high precision through a relatively simple circuit structure.

[0053] (Third Implementation)

[0054] Next, refer to Figure 4 The third embodiment will be described. Figure 4 The circuit structure of the sensor driving circuit 100-3 according to the third embodiment is shown. Hereinafter, the changes of the sensor driving circuit 100-3 according to the third embodiment compared with the sensor driving circuit 100 of the first embodiment will be described.

[0055] Figure 4 The sensor driving circuit 100-3 shown includes a first current source 110-2 and a second current source 120-2 replacing the first current source 110 and the second current source 120. The first current source 110-2 includes a polysilicon resistor 113 replacing the NMOSFET 112. The second current source 120-2 includes an NMOSFET 123 replacing the polysilicon resistor 122. That is, Figure 4 The sensor driving circuit 100-3 shown is similar to the first current source 110-2 having a polysilicon resistor 113 and the second current source 120-2 having an NMOSFET 123. Figure 1 The sensor driving circuit 100 shown is different.

[0056] Therefore, in the sensor driving circuit 100-3, the first current source 110-2 generates a first current I1a with a positive first coefficient and a positive second coefficient by applying the above voltage (Vref-Vf1) to the polysilicon resistor 113.

[0057] In addition, in the sensor driving circuit 100-3, the second current source 120-2 generates a second current I2a with a negative first coefficient and a positive second coefficient by applying the aforementioned threshold voltage Vf2 to the drain terminal of the NMOSFET 123.

[0058] Furthermore, in the sensor driving circuit 100-3, the first current I1a generated by the first current source 110-2 is added to the second current I2a generated by the second current source 120-2 to generate the third current ITCa.

[0059] In the sensor driving circuit 100-3, by adding the first coefficient (positive) of the temperature characteristic in the first current I1a to the first coefficient (negative) of the temperature characteristic in the second current I2a, the third current ITCa generated at connection point A has a relatively small (0 or near 0) first coefficient.

[0060] In addition, in the sensor driving circuit 100-3, by adding the positive quadratic coefficient of the temperature characteristic in the first current I1a to the positive quadratic coefficient of the temperature characteristic in the second current I2a, the third current ITCa generated at the connection point A has a relatively large positive quadratic coefficient.

[0061] In addition, in the sensor driving circuit 100-3, the current amplification unit 130 amplifies the third current ITCa generated by the connection point A to m times, generating the amplified current ITCa'.

[0062] in addition, Figure 4 The sensor driving circuit 100-3 shown also includes a second constant current source 142 and a connection point D. The second constant current source 142 generates a temperature-corrected second constant current Ic2 (i.e., a constant current with flat temperature characteristics). Connection point D connects the current amplification unit 130 to the second constant current source 142. Thus, connection point D subtracts the amplified current ITCa' generated by the current amplification unit 130 from the second constant current Ic2 generated by the second constant current source 142, generating a subtraction current I3 with a negative quadratic coefficient.

[0063] Furthermore, in the sensor driving circuit 100-3, the connection point B adds the subtraction current I3 generated by the connection point D to the first constant current Ic generated by the first constant current source 140 to generate the driving current Iout3 for driving the MEMS pressure sensor 12.

[0064] The sensor driving circuit 100-3 of the third embodiment, with the above-described structure, can generate a driving current (including a secondary characteristic) having a temperature characteristic opposite to the temperature characteristic of the span voltage of the MEMS pressure sensor 12, and drive the MEMS pressure sensor 12 through this driving current Iout3. Therefore, the sensor driving circuit 100-3 of the third embodiment can eliminate the secondary component of the temperature characteristic of the span voltage of the MEMS pressure sensor 12 during the analog signal processing stage. As a result, the output voltage Vout of the MEMS pressure sensor 12 is Vout≈1 / 2×π44×σ×R×Iout, where π44×R is the opposite characteristic to Iout, thus flattening the temperature characteristic. Therefore, according to the sensor driving circuit 100-3 of the third embodiment, the output error of the temperature-based MEMS pressure sensor 12 can be corrected with high precision using a relatively simple circuit structure.

[0065] (Fourth Implementation)

[0066] Next, refer to Figure 5 The fourth embodiment will be described. Figure 5 The circuit structure of the sensor driving circuit 100-4 according to the fourth embodiment is shown. Hereinafter, the changes of the sensor driving circuit 100-4 according to the fourth embodiment compared with the sensor driving circuit 100-3 according to the third embodiment will be described.

[0067] Figure 5 The sensor driving circuit 100-4 shown does not have a connection point D. Instead, the sensor driving circuit 100-4 has a connection point C between connection point A and the current amplification section 130, and a second constant current source 142 is connected to this connection point C. That is, Figure 4 The sensor drive circuit 100-3 shown has a second constant current source 142 after the current amplification section 130. In contrast, Figure 5 The sensor drive circuit 100-4 shown differs from the previous one in that it has a second constant current source 142 pre-staged in the current amplification section 130. The connection point C subtracts the third current ITCa generated by connection point A from the second constant current Ic2 generated by the second constant current source 142, resulting in a subtraction current I4 with a negative quadratic coefficient.

[0068] exist Figure 5 In the sensor driving circuit 100-4 shown, the current amplification unit 130 amplifies the subtraction current I4 generated by the connection point C by a factor of m to generate the amplified current I4'.

[0069] In addition, in the sensor driving circuit 100-4, the connection point B adds the amplified current I4' generated by the current amplification section 130 to the first constant current Ic generated by the first constant current source 140 to generate the driving current Iout4 that drives the MEMS pressure sensor 12.

[0070] The sensor driving circuit 100-4 of the fourth embodiment, through the above-described structure, can generate a subtraction current I4 with a negative quadratic coefficient by subtracting a third current ITCa with a positive quadratic coefficient from the second constant current Ic2 generated by the second constant current source 142 before amplification by the current amplification unit 130. Furthermore, the sensor driving circuit 100-4 of the fourth embodiment can amplify the subtraction current I4 by a factor of m through the current amplification unit 130 to generate an amplified current I4', and add a first constant current Ic to the amplified current I4', thereby generating a driving current Iout4 with a temperature characteristic (including a quadratic characteristic) opposite to the temperature characteristic of the span voltage of the MEMS pressure sensor 12. The MEMS pressure sensor 12 is driven by this driving current Iout4. Therefore, the sensor driving circuit 100-4 of the fourth embodiment can eliminate the quadratic component of the temperature characteristic of the span voltage of the MEMS pressure sensor 12 during the analog signal processing stage. As a result, the output voltage Vout of the MEMS pressure sensor 12 is Vout≈1 / 2×π44×σ×R×Iout, where π44×R has the opposite characteristic to Iout, and the temperature characteristic is flat. Therefore, according to the sensor driving circuit 100-4 of the fourth embodiment, the output error of the temperature-based MEMS pressure sensor 12 can be corrected with high precision through a relatively simple circuit structure.

[0071] The above describes one embodiment of the present invention in detail, but the present invention is not limited to these embodiments, and various modifications or alterations can be made within the scope of the spirit of the present invention as described in the claims.

[0072] For example, in one implementation, polysilicon resistors and NMOSFETs are used as resistors R1 and R2, which can be implemented on a single chip in a typical analog CMOS process, thus reducing the cost and probability of failure due to the reduction in the number of components. However, this is not a limitation, and other resistors (e.g., wiring resistors, thermistors, etc.) can also be used as resistors R1 and R2.

[0073] Furthermore, the circuit structure of the sensor driving circuit is not limited to the circuit structure described in one embodiment. The circuit structure of the sensor driving circuit can be any circuit structure as long as it can at least generate a driving current having a temperature characteristic opposite to the temperature characteristic of the sensor's span voltage.

[0074] Explanation of reference numerals in the attached figures

[0075] 12 MEMS pressure sensors

[0076] 14 AD converter

[0077] Sensor drive circuits for 100, 100-2, 100-3, and 100-4

[0078] 110, 110-2 First Current Source

[0079] 111 Bipolar Transistor

[0080] 112 NMOSFET (First Resistor)

[0081] 113 Polycrystalline silicon resistor

[0082] 120, 120-2 Second Current Source

[0083] 121 Bipolar Transistor

[0084] 122 Polycrystalline silicon resistor (second resistor)

[0085] 123 NMOSFET

[0086] 130 Current Amplification Section

[0087] 140 First Constant Current Source

[0088] 142 Second constant current source

[0089] 150 Fine-tuning blocks (fine-tuning section)

[0090] Connection point A (first current calculation unit)

[0091] Connection point B (Second current calculation unit)

[0092] C Connection Point

[0093] D Connection Point

[0094] I1, I1a First Current

[0095] I2, I2a Second Current

[0096] Current after subtraction of I3 and I4

[0097] ITC, ITCa Third Current

[0098] ITC2, ITC3 Fourth Current

[0099] Amplified currents from ITC', ITCa', and I4'

[0100] Ic First constant current

[0101] IC2 Second Constant Current

[0102] Iout is the drive current.

Claims

1. A sensor driving circuit, which drives a sensor with a negative first-order coefficient and a positive second-order coefficient of temperature sensitivity using current, characterized in that, The sensor driving circuit includes at least one circuit for generating a driving current for the sensor that has a temperature characteristic opposite to that of the sensor's output voltage. The sensor driving circuit includes: The first current source generates a first current with a positive primary coefficient for its temperature characteristics; The second current source generates a second current with a negative primary coefficient for its temperature characteristics; as well as The first current calculation unit adds the first current and the second current to generate a third current.

2. The sensor driving circuit according to claim 1, characterized in that, The at least one circuit includes: The first current source generates a first current with a negative quadratic coefficient for its temperature characteristics; The second current source generates a second current with a negative quadratic coefficient for its temperature characteristics; The current amplification section amplifies the third current to generate an amplified current. A constant current source that generates a temperature-corrected constant current; as well as The second current calculation unit adds the constant current to the amplified current to generate a drive current to drive the sensor.

3. The sensor driving circuit according to claim 2, characterized in that, The driving current eliminates the first and second coefficients of the temperature characteristic of the sensor's output voltage.

4. The sensor driving circuit according to claim 2 or 3, characterized in that, The sensor driving circuit includes a fine-tuning section capable of fine-tuning the first current.

5. The sensor driving circuit according to claim 2 or 3, characterized in that, The sensor driving circuit includes a fine-tuning section capable of fine-tuning the amplified current.

6. The sensor driving circuit according to claim 1, characterized in that, The sensor driving circuit includes: The first current source generates a first current with a positive quadratic coefficient for its temperature characteristics; The second current source generates a second current with a positive quadratic coefficient for its temperature characteristics; The current amplification section amplifies the third current to generate an amplified current. The first constant current source generates a temperature-corrected first constant current; The second current calculation unit generates the subtraction current by subtracting the amplified current from the first constant current; The second constant current source generates a temperature-corrected second constant current; as well as The third current calculation unit adds the current after the subtraction operation to the second constant current to generate a driving current for driving the sensor.

Images