JP4963504B2 - Sensor circuit and sensor node - Google Patents

Description

  The present invention relates to a sensor circuit used for a sensor node, and particularly to a technique for reducing the power consumption of the sensor circuit.

  FIG. 11 shows a configuration of a conventional sensor node system in which a sensor circuit for a vibration sensor that performs vibration detection is used (see, for example, Patent Document 1). The sensor node system includes a sensor node chip 50 and a receiving device 60. The sensor node chip 50 includes a sensor element 51 for detecting a physical quantity to be measured, a sensor circuit 52 for amplifying a signal detected by the sensor element 51, and detection data obtained by A / D converting the output signal of the sensor circuit 52. Output from the A / D converter 53, the CPU 54 for performing processing for compressing the detection data, for example, processing for adding chip identification information to the detection data, the memory 55 for storing the program of the CPU 54, and the CPU 54. A wireless unit 56 that wirelessly transmits detection data to the receiving device 60, and a power source 57 that supplies power to each component of the sensor node chip 50.

  A circuit diagram of a conventional sensor element 51 and sensor circuit 52 is shown in FIG. The equivalent circuit of the sensor element 51 is represented by variable capacitance elements C510 and C511 having a differential configuration and two capacitance elements C512 and C513. A contact point where the variable capacitance elements C510 and C511 are connected is connected to the ground potential, and the other contact points of the variable capacitance elements C510 and C511 are connected to the power supply potential via the capacitance elements C512 and C513, respectively. A contact point between the variable capacitance element C510 and the capacitance element C512 is connected to a non-inverting input terminal of the differential amplifier A520 constituting the sensor circuit 52, and a contact point between the variable capacitance element C511 and the capacitance element C513 is connected to the differential amplifier A520. It is connected to the inverting input terminal.

  Operations of the sensor element 51 and the sensor circuit 52 will be described. The variable capacitance elements C510 and C511 are formed with a fine structure on the silicon chip by a MEMS process. Specifically, it has a fixed electrode and a movable electrode. When the movable electrode moves due to vibration applied from the outside and the distance between the electrodes changes, the capacitance changes. Here, the electrostatic capacitances of the two variable capacitance elements C510 and C511 change in a differential manner. The voltage at the contact point between the variable capacitance element C510 and the capacitance element C512 is a voltage obtained by dividing the power supply voltage by the respective capacitance values of the variable capacitance element C510 and the capacitance element C512. Similarly, the voltage at the contact point between the variable capacitance element C511 and the capacitance element C513 is a voltage obtained by dividing the power supply voltage by the respective capacitance values of the variable capacitance element C511 and the capacitance element C513. Since the capacitances of the variable capacitance elements C510 and C511 change differentially, the differential signal is input to the differential amplifier A520, and the amplified signal is output from the differential amplifier A520.

Japanese Patent Laid-Open No. 2004-024551

  When the sensor circuit shown in FIG. 12 is applied to the sensor node system shown in FIG. 11, since a steady current continues to flow through the sensor circuit while detecting a physical quantity such as external vibration, the sensor node system operates with a limited energy source. There is a problem that the operation time of the sensor node chip to be shortened.

  The present invention has been made to solve the above-described problems, and an object thereof is to reduce the power consumption of a sensor circuit.

  In the sensor circuit (first embodiment) of the present invention, the input terminal is connected to the first common potential, and the output terminal is connected to the first output terminal of the sensor element that outputs a differential signal according to the physical quantity. And a first output terminal connected to an output terminal of the first diode and a first output terminal of the sensor element, and an output terminal connected to a second output terminal of the sensor element. A second diode, an input terminal connected to an output terminal of the second diode and a second output terminal of the sensor element, and an output terminal connected to an output terminal of the sensor circuit; And the capacitor connected to the output terminal of the sensor circuit, the second terminal connected to the second common potential, and the voltage of the output terminal of the sensor circuit at the time of initialization to the second common potential. The first initialization It is characterized in further comprising a pitch.

In one configuration example (second embodiment) of the sensor circuit of the present invention, each of the first, second, and third diodes includes a first control terminal connected to a first control terminal. It is characterized by comprising second and third first polarity transistors.
In one configuration example (third embodiment) of the sensor circuit of the present invention, each of the first, second, and third first polarity transistors has a second control terminal that is an output of the first polarity transistor. It is connected to a terminal.
In one configuration example (fourth embodiment) of the sensor circuit of the present invention, the first, second, and third first polarity transistors have a second control terminal as an output terminal of the sensor circuit. It is characterized by being connected.
Further, in one configuration example (fifth embodiment) of the sensor circuit of the present invention, the input terminal and the first control terminal are further connected to the first common potential, and the output terminal is the first and second terminals. 2, a fourth first polarity transistor connected to a third control terminal of the third first polarity transistor, and a third control of the first, second, and third first polarity transistors at the time of initialization And a second initialization switch for setting the terminal to the second common potential, and the third control terminal of the first, second, and third first polarity transistors is extracted from the second control terminal. The second impurity region is formed outside the first impurity region.

Further, in the configuration example (sixth embodiment) of the sensor circuit of the present invention, the input terminal and the first control terminal are further connected to the output terminal of the sensor circuit, and the output terminal is the first and second terminals. 2 and a fourth first polarity transistor connected to a second control terminal of the third first polarity transistor, the third control terminal of the first, second and third first polarity transistors being The second control terminal is extracted from a second impurity region formed outside the first impurity region from which the second control terminal is extracted, and is connected to the first common potential.
In one configuration example (seventh embodiment) of the sensor circuit of the present invention, the third control terminal of the first, second, and third first polarity transistors is the second control terminal. It is extracted from a second impurity region formed outside the first impurity region to be extracted and connected to the output terminal of the sensor circuit.
Further, in one configuration example (eighth embodiment) of the sensor circuit of the present invention, the first, second, and third diodes each have a first control terminal connected to a first control terminal. It is characterized by comprising second and third second polarity transistors.
The sensor node of the present invention is characterized by mounting a sensor circuit.

  According to the present invention, the first common potential is set by alternately turning on the first diode and the third diode and the second diode according to the output of the sensor element. To the second common potential can be reduced to about the leakage current of the diode (sub-microamperes or less). As a result, if the sensor circuit of the present invention is used, the power consumption of the sensor node chip can be reduced to the nanowatt level limit. Therefore, it is not necessary to increase the power generation amount of the power supply unit of the sensor node chip, and the volume of the power generation mechanism can be reduced. Therefore, downsizing of the sensor node chip is achieved, and the sensor node chip can be embedded also in an object or a human part that could not be embedded due to size restrictions until now. Furthermore, the range of ubiquitous network services using the sensor node system can be expanded, and services with improved user convenience can be provided, which is highly effective.

  Further, in the present invention, when the second control terminal of the first, second, and third first polarity transistors is connected to the output terminal of the first polarity transistor, for example, vibration is detected as a physical quantity. Can be detected with a higher sensitivity.

  In the present invention, the circuit area can be reduced by connecting the second control terminal of the first, second, and third first polarity transistors to the output terminal of the sensor circuit.

  In the present invention, the input terminal and the first control terminal are connected to the first common potential, and the output terminal is connected to the third control terminal of the first, second, and third first polarity transistors. By providing a fourth first polarity transistor and a second initialization switch that sets the third control terminal of the first, second, and third first polarity transistors to the second common potential at the time of initialization. For example, in the case where vibration is detected as a physical quantity, it is possible to reduce a phenomenon that charges flow into the capacitor element regardless of a detection signal due to vibration.

  In the present invention, the input terminal and the first control terminal are connected to the output terminal of the sensor circuit, and the output terminal is connected to the second control terminal of the first, second, and third first polarity transistors. By providing the fourth first polarity transistor, for example, when vibration is detected as a physical quantity, it is possible to reduce a phenomenon that charges flow into the capacitor element regardless of a detection signal due to vibration.

  In the present invention, the third control terminal of the first, second, and third first polarity transistors is connected to the output terminal of the sensor circuit, thereby connecting the third control terminal to the first common potential. In this case, the electric charge flowing in the capacitor element can be suppressed.

  In the present invention, the first, second, and third diodes are configured by first, second, and third second polarity transistors each having a first control terminal connected to the output terminal. For example, in the case of detecting vibration as a physical quantity, even if the vibration is small, the sensitivity can be detected with high sensitivity.

It is a circuit diagram showing composition of a sensor element and a sensor circuit concerning a 1st embodiment of the present invention. It is a figure which shows the operation | movement waveform of each part of the sensor circuit which concerns on the 1st Embodiment of this invention. It is a circuit diagram which shows the structure of the sensor element and sensor circuit which concern on the 2nd Embodiment of this invention. It is a circuit diagram which shows the structure of the sensor element and sensor circuit which concern on the 3rd Embodiment of this invention. It is a circuit diagram which shows the structure of the sensor element and sensor circuit which concern on the 4th Embodiment of this invention. It is sectional drawing which shows the structure of an NMOS transistor. It is a circuit diagram which shows the structure of the sensor element and sensor circuit which concern on the 5th Embodiment of this invention. It is a circuit diagram which shows the structure of the sensor element and sensor circuit which concern on the 6th Embodiment of this invention. It is a circuit diagram which shows the structure of the sensor element which concerns on the 7th Embodiment of this invention, and a sensor circuit. It is a circuit diagram which shows the structure of the sensor element which concerns on the 8th Embodiment of this invention, and a sensor circuit. It is a block diagram which shows the structure of the conventional sensor node system. It is a circuit diagram which shows the structure of the conventional sensor element and sensor circuit.

[First Embodiment]
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a circuit diagram showing a configuration of a sensor element and a sensor circuit according to the first embodiment of the present invention.
The variable capacitance elements VC1 and VC2 having a differential configuration shown in FIG. A contact point to which the variable capacitance elements VC1 and VC2 are connected is connected to the ground potential. The variable capacitance elements VC1 and VC2 are formed with a fine structure on a silicon chip by a MEMS process, and each have a fixed electrode and a movable electrode. When the movable electrode moves due to vibration applied from the outside and the distance between the electrodes changes, the capacitance changes. The capacitances of the two variable capacitance elements VC1 and VC2 change in a differential manner according to vibration applied from the outside.

  The sensor circuit 2 includes a first diode D1 whose anode terminal is connected to the power supply potential VDD, a cathode terminal connected to the first output terminal 10 of the sensor element 1, and an anode terminal that is the cathode terminal of the first diode D1. The second diode D2 is connected to the first output terminal 10 of the sensor element 1, the cathode terminal is connected to the second output terminal 11 of the sensor element 1, and the anode terminal is the cathode terminal of the second diode D2. And the third diode D3 connected to the second output terminal 11 of the sensor element 1, the cathode terminal connected to the output terminal OUT of the sensor circuit 2, the first terminal connected to the output terminal OUT, and the second The capacitor C1 whose terminal is connected to the ground potential, the first terminal is connected to the output terminal OUT, the second terminal is connected to the ground potential, and the control terminal is initialized. Composed of connected initialization switch SW1 Metropolitan child RST.

  The operation of the sensor circuit 2 according to the present embodiment will be described with reference to FIG. When the sensor element 1 and the sensor circuit 2 of the present embodiment are applied to the sensor node chip shown in FIG. 11, the initial value given to the initialization terminal RST from the control circuit (not shown) when the sensor node chip before the time T0 is initialized. The initialization switch SW1 is turned on by the activation signal, and the charge of the capacitive element C1 is discharged. Thereafter, the control circuit turns off the initialization switch SW1, and the sensor circuit 2 enters an input waiting state.

  When vibration is applied to the sensor node chip at time T0, the capacitances of the two variable capacitance elements VC1 and VC2 of the sensor element 1 change differentially. At this time, since the movable electrode of the variable capacitance element VC1 approaches or moves away from the fixed electrode in response to vibration, the capacitance of the variable capacitance element VC1 repeats increasing and decreasing alternately. Therefore, the detection signal BP output from the first output terminal 10 of the sensor element 1 is a signal that alternately repeats increasing and decreasing as shown in FIG. Similarly, the detection signal BN output from the second output terminal 11 of the sensor element 1 is a signal that alternately repeats increasing and decreasing as shown in FIG. As described above, since the electrostatic capacitances of the variable capacitance elements VC1 and VC2 change differentially, the phases of the detection signals BP and BN differ by 180 °.

  When the detection signal BP is High and the detection signal BN is Low, the first diode D1 and the third diode D3 are turned off, and when the detection signal BP is Low and the detection signal BN is High, the first diode D1 and the third diode D3 The diode D3 is turned on. On the other hand, when the detection signal BP is High and the detection signal BN is Low, the second diode D2 is turned on, and when the detection signal BP is Low and the detection signal BN is High, the second diode D2 is turned off. As described above, the pair of the first diode D1 and the third diode D3 and the second diode D2 are alternately turned on by the detection signals BP and BN, and electric charges are gradually accumulated in the capacitive element C1, The voltage of the output signal SO of the sensor circuit 2 rises (FIG. 2C).

  The A / D converter 53 of the sensor node chip 50 shown in FIG. 11 performs threshold processing on the output signal SO of the sensor circuit 2 and outputs a control signal as shown in FIG. In the example of FIGS. 2C and 2D, the output signal SO of the sensor circuit 2 becomes equal to or greater than the threshold at time T1 after ΔT1 from time T0, so that the control signal output from the A / D conversion unit 53 Becomes High.

  As described above, in the present embodiment, according to the output of the sensor element 1, the set of the first diode D1 and the third diode D3 and the second diode D2 are alternately turned on. As a result, the direct current flowing from the power supply potential VDD to the ground potential can be reduced to about the leakage current of the diode (sub-microamperes or less). Therefore, if the sensor element 1 and the sensor circuit 2 of the present embodiment are used, the power of the sensor node chip on which the sensor element 1 and the sensor circuit 2 are mounted can be reduced to the limit of nanowatt level.

[Second Embodiment]
Next, a second embodiment of the present invention will be described. FIG. 3 is a circuit diagram showing a configuration of a sensor element and a sensor circuit according to the second embodiment of the present invention.
In the present embodiment, as specific examples of the first, second, and third diodes D1, D2, and D3 of the first embodiment, a first, second, The third NMOS transistors Q1, Q2, and Q3 are used.

The gate terminal G and drain terminal D of the first NMOS transistor Q 1 are connected to the power supply potential VDD, and the source terminal S is connected to the first output terminal 10 of the sensor element 1. The gate terminal G and the drain terminal D of the second NMOS transistor Q2 are connected to the source terminal S of the first NMOS transistor Q1 and the first output terminal 10 of the sensor element 1, and the source terminal S is the second terminal of the sensor element 1. Are connected to the output terminal 11. The gate terminal G and the drain terminal D of the third NMOS transistor Q3 are connected to the source terminal S of the second NMOS transistor Q2 and the second output terminal 11 of the sensor element 1, and the source terminal S is the output terminal of the sensor circuit 2. Connected to OUT. Other configurations are the same as those of the first embodiment.
Thus, in this embodiment, the effects described in the first embodiment can be obtained.

[Third Embodiment]
Next, a third embodiment of the present invention will be described. FIG. 4 is a circuit diagram showing a configuration of a sensor element and a sensor circuit according to the third embodiment of the present invention.
In the second embodiment, the body terminals B of the NMOS transistors Q1, Q2, and Q3 are connected to the source terminals S of the NMOS transistors Q1, Q2, and Q3, respectively, in the second embodiment.

  Since the voltage at the source terminal S of each NMOS transistor Q1, Q2, Q3 is higher than the ground potential, the threshold voltage of the NMOS transistors Q1, Q2, Q3 decreases due to the body bias effect of the MOS transistor, and transition between the on state and the off state Is easier to do. That is, even if the change amount of the electrostatic capacitances of the variable capacitance elements VC1 and VC2 of the sensor element 1 is small, it is possible to store charges in the capacitance element C1. As a result, in the present embodiment, the sensitivity of vibration detection can be improved.

[Fourth Embodiment]
Next, a fourth embodiment of the present invention will be described. FIG. 5 is a circuit diagram showing a configuration of a sensor element and a sensor circuit according to the fourth embodiment of the present invention.
In the third embodiment, the body terminal B of the NMOS transistors Q1, Q2, and Q3 is connected to the output terminal OUT of the sensor circuit 2 in the third embodiment.

  In the present embodiment, the body terminals B of the NMOS transistors Q1, Q2, and Q3 can be shared as compared with the third embodiment, and one terminal can be drawn from the NMOS transistors Q1, Q2, and Q3. Therefore, the circuit area can be reduced.

[Fifth Embodiment]
Next, a fifth embodiment of the present invention will be described. A cross-sectional view of the NMOS transistor is shown in FIG. In FIG. 6, 60 is a P-type body, 61 is an N-type well, 62 is an N-type region connected to the drain terminal D, 63 is an N-type region connected to the source terminal S, and 64 is a gate terminal G. An electrode to be connected, 65 is a P ⁺ type region connected to the body terminal B, and 66 is an N ⁺ type region connected to the well terminal W.

  In a normal CMOS, an N-type well 61 is formed outside a P-type body 60, and a well terminal W is connected to a power supply potential VDD. Accordingly, when the body terminal B is set to an intermediate potential between the power supply potential VDD and the ground potential as in the fourth embodiment, the reverse bias voltage of the PN junction connected between the body 60 and the well 61 is set. Since an unintended current flows between the well 61 and the body 60, electric charge flows from the power supply potential VDD into the capacitive element C1 regardless of a detection signal due to vibration.

  The present embodiment solves such a problem. FIG. 7 is a circuit diagram showing the configuration of the sensor element and the sensor circuit according to the present embodiment. In the present embodiment, in addition to the fourth embodiment, the gate terminal G and the drain terminal D are connected to the power supply potential VDD, and the source terminal S is connected to the common well terminal W of the NMOS transistors Q1, Q2, and Q3. And an initialization switch SW2 in which the first terminal is connected to the well terminal W, the second terminal is connected to the ground potential, and the control terminal is connected to the initialization terminal RST. Is provided. Note that D4 in FIG. 7 represents a diode formed between the body terminal B and the well terminal W of the NMOS transistors Q1, Q2, and Q3, and does not mean that a diode is newly inserted. Absent.

  The operation of this embodiment will be described. Similar to the first embodiment, the initialization switches SW1 and SW2 are turned on by an initialization signal supplied from the control circuit (not shown) to the initialization terminal RST when the sensor node chip is initialized. The switch SW1 and SW2 are turned off, and the sensor circuit 2 enters an input waiting state. At this time, the well terminals W of the NMOS transistors Q1, Q2, and Q3 are set to a potential that is lowered from the power supply potential VDD by the threshold voltage of the diode-connected NMOS transistor Q4. The operation of detecting vibration by the sensor element 1 and the sensor circuit 2 is as described in the first embodiment.

  In the present embodiment, the current flowing from the wells of the NMOS transistors Q1, Q2, Q3 to the body can be reduced as compared with the case where the well terminals W of the NMOS transistors Q1, Q2, Q3 are connected to the power supply potential VDD. Therefore, it is possible to reduce the phenomenon that charges flow into the capacitive element C1 regardless of the detection signal due to vibration.

[Sixth Embodiment]
Next, a sixth embodiment of the present invention will be described. FIG. 8 is a circuit diagram showing a configuration of a sensor element and a sensor circuit according to the sixth embodiment of the present invention.
In the present embodiment, in the fourth embodiment, the gate terminal G and the drain terminal D are further connected to the output terminal OUT of the sensor circuit 2, and the source terminal S is the body terminal B of the NMOS transistors Q1, Q2, Q3. And a fourth NMOS transistor Q5 connected to the. As in the case of FIG. 7, D4 in FIG. 8 represents a diode formed between the body terminal B and the well terminal W of the NMOS transistors Q1, Q2, and Q3, and a diode is newly inserted. It doesn't mean that.

  In this embodiment, even when a current flows from the well terminal W of the NMOS transistors Q1, Q2, and Q3 to the body terminal B, the charge flowing into the output terminal OUT is reduced by inserting the diode-connected NMOS transistor Q5. Can be suppressed. As a result, in the present embodiment, as in the fifth embodiment, it is possible to reduce the phenomenon that charges flow into the capacitive element C1 regardless of the detection signal due to vibration.

[Seventh Embodiment]
Next, a seventh embodiment of the present invention will be described. FIG. 9 is a circuit diagram showing a configuration of a sensor element and a sensor circuit according to the seventh embodiment of the present invention.
In the fourth embodiment, the well terminals W of the NMOS transistors Q1, Q2, and Q3 are connected to the output terminal OUT of the sensor circuit 2 in the fourth embodiment. In the present embodiment, by setting the well potential of the NMOS transistors Q1, Q2, and Q3 to the same potential as the body potential, the capacitor element C1 when the well terminal W of the NMOS transistors Q1, Q2, and Q3 is connected to the power supply potential VDD. It is possible to suppress the charge flowing in

[Eighth Embodiment]
Next, an eighth embodiment of the present invention will be described. FIG. 10 is a circuit diagram showing a configuration of a sensor element and a sensor circuit according to the eighth embodiment of the present invention.
In the second embodiment, diode-connected PMOS transistors Q6, Q7, and Q8 are used instead of the diode-connected NMOS transistors Q1, Q2, and Q3 in the second embodiment.

  Since the body terminal of the PMOS transistor is connected to the power supply potential VDD, the body bias effect can be reduced as compared to the NMOS transistor, and the threshold voltage of the diode connection can be lowered. It becomes easier to do. In a CMOS configuration, when a buried channel transistor is used for the PMOS, it is common to lower the threshold voltage of the PMOS in order to match the saturation current with that of the NMOS transistor. Therefore, by using a PMOS transistor instead of a diode-connected NMOS transistor, the threshold voltage of the diode connection can be lowered, and the transition between the on state and the off state is facilitated. That is, even if the amount of change in capacitance of the variable capacitance elements VC1 and VC2 of the sensor element 1 is small, charges can be stored in the capacitance element C1, and vibration detection is performed as in the third embodiment. The sensitivity can be improved.

  In the first to eighth embodiments, the case where the sensor element 1 and the sensor circuit 2 are used for vibration detection is described. However, the present invention is not limited to this, and the present invention is applied to other than vibration detection. Is also possible.

  The present invention can be applied to a sensor circuit used for a sensor node.

  DESCRIPTION OF SYMBOLS 1 ... Sensor element, 2 ... Sensor circuit, VC1, VC2 ... Variable capacitance element, D1, D2, D3 ... Diode, Q1, Q2, Q3, Q4, Q5 ... NMOS transistor, Q6, Q7, Q8 ... PMOS transistor, C1 ... Capacitance elements, SW1, SW2,... Initialization switch.

Claims (9)

A first diode having an input terminal connected to a first common potential and an output terminal connected to a first output terminal of a sensor element that outputs a differential signal according to a physical quantity;
A second diode having an input terminal connected to the output terminal of the first diode and the first output terminal of the sensor element, and an output terminal connected to the second output terminal of the sensor element;
A third diode having an input terminal connected to the output terminal of the second diode and the second output terminal of the sensor element, and an output terminal connected to the output terminal of the sensor circuit;
A capacitive element having a first terminal connected to the output terminal of the sensor circuit and a second terminal connected to a second common potential;
A sensor circuit, comprising: a first initialization switch that sets a voltage at an output terminal of the sensor circuit at the time of initialization to the second common potential. The sensor circuit according to claim 1.
The first, second, and third diodes are constituted by first, second, and third first polarity transistors each having a first control terminal connected to an input terminal. . The sensor circuit according to claim 2,
Each of the first, second, and third first polarity transistors has a second control terminal connected to an output terminal of the first polarity transistor. The sensor circuit according to claim 2,
The first, second, and third first polarity transistors have a second control terminal connected to an output terminal of the sensor circuit. The sensor circuit according to claim 4, wherein
Furthermore, the input terminal and the first control terminal are connected to the first common potential, and the output terminal is connected to the third control terminal of the first, second, and third first polarity transistors. A first polarity transistor of
A second initialization switch that sets the third control terminal of the first, second, and third first polarity transistors at the time of initialization to the second common potential;
A third control terminal of the first, second, and third first polarity transistors is extracted from a second impurity region formed outside the first impurity region from which the second control terminal is extracted. A sensor circuit characterized by that. The sensor circuit according to claim 4, wherein
Furthermore, the input terminal and the first control terminal are connected to the output terminal of the sensor circuit, and the output terminal is connected to the second control terminal of the first, second, and third first polarity transistors. A first polarity transistor of
The third control terminal of the first, second, and third first polarity transistors is extracted from a second impurity region formed outside the first impurity region from which the second control terminal is extracted. A sensor circuit connected to the first common potential. The sensor circuit according to claim 4, wherein
The third control terminal of the first, second, and third first polarity transistors is extracted from a second impurity region formed outside the first impurity region from which the second control terminal is extracted. A sensor circuit connected to an output terminal of the sensor circuit. The sensor circuit according to claim 1.
The first, second, and third diodes are constituted by first, second, and third polarity transistors each having a first control terminal connected to an output terminal. .   A sensor node comprising the sensor circuit according to claim 1.

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