JP2013148488A - Detection circuit, sensor device, and electronic apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a detection circuit capable of reducing a variation in output voltage caused by a variation in element characteristics, a sensor device, and an electronic apparatus.SOLUTION: A detection circuit comprises: a pyroelectric element 10; a first P-type transistor TP1 that is provided between an output node NQ and a low potential power source node of the detection circuit, and in which a detection signal from the pyroelectric element 10 is input to a gate; and a second P-type transistor TP2 that is provided between a high potential power source node and the output node NQ, and in which the gate is set to a reference voltage VR. When a voltage of the high potential power source node is Vcc, and a voltage of the low potential power source node is GND, the reference voltage is set to Vcc/2.

Description

  The present invention relates to a detection circuit, a sensor device, an electronic device, and the like.

  Conventionally, an infrared detection circuit using a pyroelectric element or the like is known. For example, infrared rays having a wavelength in the vicinity of 10 μm are radiated from the human body, and by detecting this, information on the presence and temperature of the human body can be acquired without contact. Therefore, intrusion detection and physical quantity measurement can be realized by using such an infrared detection circuit.

  As conventional techniques of infrared detection circuits, for example, techniques disclosed in Non-Patent Document 1 and Patent Document 1 are known. In the prior art of Non-Patent Document 1, the pyroelectric current of a pyroelectric element is detected by a source follower circuit including a transistor (JFET) and a resistor connected in series.

  In the prior art of Patent Document 1, a P-type transistor that functions as a load element and an N-type transistor that functions as an amplifying element are connected in series to form a common-source amplifier circuit. The pyroelectric current of the element is detected.

JP 2009-68863 A

Daisuke Akai et al., “Pyroelectric infrared sensors with fast response time and high sensitivity using epitaxial PbZr, TiO3 films on epitaxial γ-Al2O3 / Si substrates”, Sensors and Actuators A: Physical, Volumes 130-131, 14 August 2006, Pages 111-115, Elsevier Science BV

  However, these conventional techniques have a problem that the variation in output voltage of the detection circuit becomes very large due to variations in characteristics of circuit elements such as resistors and transistors constituting the detection circuit.

  According to some aspects of the present invention, it is possible to provide a detection circuit, a sensor device, an electronic apparatus, and the like that can reduce variations in output voltage caused by variations in element characteristics.

  (1) In one embodiment of the present invention, a pyroelectric element is provided between an output node of a detection circuit and a low-potential power supply node, and a detection signal from the pyroelectric element is input to a gate. And a second P-type transistor provided between a high-potential power supply node and the output node and having a gate set to a reference voltage, the voltage of the high-potential power supply node being Vcc, When the voltage of the low potential power supply node is GND, the reference voltage relates to a detection circuit set to Vcc / 2.

  According to one aspect of the present invention, there are a pyroelectric element, a first P-type transistor in which a detection signal from the pyroelectric element is input to a gate, and a second P-type transistor in which the gate is set to a reference voltage. Provided. The first and second P-type transistors constitute a source follower circuit, and an output voltage corresponding to the detection signal input to the gate of the first P-type transistor is output to the output node. According to the detection circuit having such a configuration, the influence of the characteristic variation such as the threshold voltage of the first and second P-type transistors on the output voltage can be suppressed. The variation in output voltage can be reduced.

  Moreover, under the condition that the threshold voltages of the first and second P-type transistors are substantially equal, the gate voltage of the first P-type transistor connected to the pyroelectric element is SD, and the output node of the detection circuit When the voltage is VQ, VQ = Vcc / 2 + SD, and the fluctuation voltage SD accompanying the pyroelectric current in the pyroelectric element is detected by comparing with the reference voltage Vcc / 2 which is the gate voltage of the first P-type transistor. It becomes easy.

  (2) In one aspect of the present invention, it may further include a differential amplifier circuit that receives the voltage of the output node and the reference voltage Vcc / 2 and performs differential amplification.

  The comparison voltage of the differential amplifier circuit can be the reference voltage Vcc / 2, which is the gate voltage of the second P-type transistor, and the fluctuation voltage SD accompanying the pyroelectric current in the pyroelectric element is output from the differential amplifier circuit. As accurately as you can get. This differential amplifier circuit can be provided in common with other pyroelectric element detection circuits.

  (3) In one aspect of the present invention, the output node can be connected to the gate of the second P-type transistor.

  In the steady state of the pyroelectric element, the voltage SD accompanying the pyroelectric current is close to 0 V, in which case VQ≈VCC / 2, and Vcc / 2 can be supplied to the gate of the second P-type transistor. In addition, in this case, it is not necessary to provide a separate reference voltage generation circuit, so that the detection circuit can be reduced in size.

(4) In one mode of the present invention, it further has a reference voltage generation circuit which generates the above-mentioned reference voltage,
The reference voltage generation circuit includes a third P-type transistor and a fourth P-type transistor connected in series between the high-potential power supply node and the low-potential power supply node,
A connection node between the source of the third P-type transistor with the low-potential power supply node connected to the drain and the drain of the fourth P-type transistor with the high-potential power supply node connected to the source is the reference The output node of the voltage generator circuit,
In the third P-type transistor, the low power supply node is connected to a gate,
The fourth P-type transistor can connect an output node of the reference voltage generation circuit to a gate.

  As described above, the third and fourth P-type transistors of the reference voltage generation circuit that generates the reference voltage Vcc / 2 have the same configuration as the first and second P-type transistors of the source follower circuit, and there is a process variation. However, since it varies in the same tendency as the first and second P-type transistors, the relative variation is eliminated, and an output with less dependence on process variation can be secured. In particular, if the first to fourth P-type transistors have the same size, the influence of process variations can be minimized.

(5) Another aspect of the present invention is:
A pyroelectric element;
A first P-type transistor provided between an output node of the detection circuit and a low-potential power supply node, wherein a detection signal from the pyroelectric element is input to a gate;
A second P-type transistor provided between a high-potential power supply node and the output node and having a gate set to a reference voltage;
A reference voltage generating circuit for generating the reference voltage;
Have
The reference voltage generation circuit includes a third P-type transistor and a fourth P-type transistor connected in series between the high-potential power supply node and the low-potential power supply node,
A connection node between the source of the third P-type transistor with the low-potential power supply node connected to the drain and the drain of the fourth P-type transistor with the high-potential power supply node connected to the source is the reference The output node of the voltage generator circuit,
In the third P-type transistor, the low-potential power supply node is connected to the gate,
The fourth P-type transistor relates to a detection circuit in which an output node of the reference voltage generation circuit is connected to a gate.

  In another aspect of the present invention, the influence of the characteristic variation such as the threshold voltage of the first and second P-type transistors on the output voltage can be suppressed, so that the output voltage caused by the variation in the element characteristic can be reduced. Variations can be reduced. In addition, the third and fourth P-type transistors of the reference voltage generating circuit have the same configuration as the first and second P-type transistors of the source follower circuit, and the first and second P-type transistors can be used even if there are process variations. Since the tendency is the same as that of the type transistor, the variation is relatively eliminated, and an output with less dependence on process variation can be secured.

  (6) In another aspect of the present invention, the substrate potential of the first P-type transistor is set to the source potential of the first P-type transistor, and the substrate potential of the second P-type transistor is The potential of the source of the second P-type transistor may be set.

  In this way, fluctuations in the threshold voltage of the first and second P-type transistors due to the substrate bias effect can be prevented, so that variations in output voltage can be further reduced.

  (7) In another aspect of the invention, the substrate potential of the first P-type transistor is set to the potential of the output node of the reference voltage generation circuit, and the substrate potential of the second P-type transistor is It may be set to the source potential of the second P-type transistor.

  Thus, the first P-type transistor can output the voltage SD accompanying the pyroelectric current in the pyroelectric element close to the gain of 1.

  (8) In another aspect of the present invention, the reference voltage generation circuit may be shared with a detection circuit of another pyroelectric element.

  Thus, if the reference voltage generation circuit is shared, the layout area of the transistor can be reduced.

(9) Still another aspect of the present invention provides:
A pyroelectric element;
A first P-type transistor and a second P-type transistor connected in series between a high potential power supply node and a low potential power supply node;
A detection circuit comprising:
A connection node between the source of the first P-type transistor with the low-potential power supply node connected to the drain and the drain of the second P-type transistor with the high-potential power supply node connected to the source is the detection The output node of the circuit,
In the first P-type transistor, a detection signal from the pyroelectric element is input to a gate,
The second P-type transistor relates to a detection circuit in which an output node of the detection circuit is connected to a gate.

  In still another aspect of the present invention, the gate voltage of the first P-type transistor connected to the pyroelectric element is SD under the condition that the threshold voltages of the first and second P-type transistors are substantially equal. When the voltage at the output node of the detection circuit is VQ, VQ = (Vcc + SD) / 2. In the steady state of the pyroelectric element, the voltage SD accompanying the pyroelectric current is close to 0 V, in which case VQ≈VCC / 2, and Vcc / 2 is supplied to the gate of the first P-type transistor, as in one embodiment of the present invention. be able to.

  (10) In still another aspect of the present invention, the substrate potential of the first P-type transistor is set to the source potential of the first P-type transistor, and the substrate potential of the second P-type transistor is The potential of the source of the second P-type transistor may be set.

  In this way, fluctuations in the threshold voltage of the first and second P-type transistors due to the substrate bias effect can be prevented, so that variations in output voltage can be further reduced.

  In each of the above aspects of the present invention, the first P-type transistor and the second P-type transistor may have the same gate length or gate width.

  In this way, it becomes possible to make the device characteristics such as the threshold voltage of the first and second P-type transistors close to each other, and the variation in output voltage can be further reduced.

  In each of the above aspects of the present invention, the first P-type transistor and the second P-type transistor may be laid out adjacent to each other.

  If the layout is arranged in this way, variations in element characteristics of the first and second P-type transistors due to manufacturing process variations and the like can be reduced, and variations in output voltage can be further reduced.

  (11) Still another embodiment of the present invention relates to a sensor device including any one of the detection circuits described above.

  (12) Still another aspect of the present invention provides a sensor array in which a plurality of sensor cells are arranged, a plurality of row lines, one or a plurality of column lines, and a row selection connected to the plurality of row lines. A readout circuit connected to the one or more column lines, each sensor cell of the plurality of sensor cells is a pyroelectric element, and an output node to a corresponding column line corresponding to each sensor cell; A first P-type transistor provided between a low-potential power supply node and a detection signal from the pyroelectric element is input to a gate; and provided between a high-potential power supply node and the output node; A second P-type transistor set to a reference voltage, where the reference voltage is set to Vcc / 2 when the voltage of the high potential power supply node is Vcc and the voltage of the low potential power supply node is GND. Sensor Related to the device.

  According to still another aspect of the present invention, variation in output voltage from the sensor cell can be reduced in the same manner as in one aspect of the present invention.

  (13) According to another aspect of the present invention, a sensor array in which a plurality of sensor cells are arranged, a plurality of row lines, one or a plurality of column lines, and a row selection circuit connected to the plurality of row lines. A readout circuit connected to the one or more column lines, and a current source circuit connected to the one or more column lines, each sensor cell of the plurality of sensor cells comprising a pyroelectric element A first P-type transistor provided between an output node to a corresponding column line corresponding to each sensor cell and a low-potential power supply node and receiving a detection signal from the pyroelectric element at a gate. The current source circuit is provided between a high potential power supply node and the corresponding column line, a gate is set to a reference voltage, and a current is supplied to each sensor cell via the corresponding column line. Including a P-type transistor, The voltage of the node and Vcc, said when the voltage GND to the low-potential power supply node, said reference voltage is related to the sensor device that is set to Vcc / 2.

  According to another aspect of the present invention, a source follower circuit is configured by the first P-type transistor of each sensor cell and the second P-type transistor of the current source circuit. It is possible to reduce variations in output voltage from the.

  (14) In still another aspect of the invention, each sensor cell is provided between the output node and the corresponding column line, and a corresponding row line corresponding to each sensor cell is connected to a gate. Each sensor cell of a plurality of sensor cells including a row selection transistor and provided corresponding to the corresponding column line may be connected to the corresponding column line via the row selection transistor.

  In this way, by performing on / off control of the row selection transistor by the corresponding row line, each sensor cell is connected to the corresponding column line via the row selection transistor, and the output voltage can be read out.

  (15) Another aspect of the invention relates to an electronic apparatus including the detection circuit according to any one of the above.

  (16) Moreover, the other aspect of this invention is related with the electronic device containing the sensor device in any one of said.

It is explanatory drawing of the detection circuit of a comparative example. It is a characteristic figure of subject temperature-output voltage of a detection circuit of a comparative example. It is a block diagram of the detection circuit of this embodiment. It is a figure which shows the hysteresis loop of a pyroelectric element. It is a characteristic diagram of subject temperature-output voltage of the detection circuit of the present embodiment. It is a figure which shows the modification of the detection circuit of this embodiment. It is a figure which shows the other modification of the detection circuit of this embodiment. It is a characteristic figure of subject temperature-output voltage of a detection circuit of a modification. 9A and 9B are configuration diagrams of the sensor device. It is a detailed 1st lineblock diagram of a sensor device. It is a 2nd detailed block diagram of a sensor device. It is a block diagram of the electronic device of this embodiment. It is a figure which shows the body temperature measuring apparatus (electronic device) containing a terahertz camera. It is a perspective view of a terahertz camera. It is a block diagram of a terahertz camera.

  Hereinafter, preferred embodiments of the present invention will be described in detail. The present embodiment described below does not unduly limit the contents of the present invention described in the claims, and all the configurations described in the present embodiment are indispensable as means for solving the present invention. Not necessarily.

1. Comparative Example FIG. 1 shows a conventional circuit configuration of Non-Patent Document 1 described above as a comparative example. The detection circuit of this comparative example includes a pyroelectric element 10, an N-type depletion transistor TN, and a resistor R.

  CP is the capacitance of the pyroelectric element 10, and RP is the resistance of the pyroelectric element 10. Infrared light is incident on the pyroelectric element 10, and spontaneous polarization corresponding to the temperature of the pyroelectric element 10 is generated in the pyroelectric body (ferroelectric material) 11 of the pyroelectric element 10. And it is electrically neutral with the surface charges of the electrodes 12 and 13.

  An N-type depletion transistor TN and a resistor R are provided in series between a VCC node (high-potential power supply node in a broad sense) and a GND node (low-potential power supply node in a broad sense) to form a source follower circuit. Has been.

  The detection signal SD (detection voltage) from the pyroelectric element 10 is input to the gate of the N-type transistor TN, and the source of the N-type transistor TN is connected to one end of the resistor R. These transistors TN and resistors R constitute a source follower circuit, and its gain is almost 1. An output voltage VQ that changes with a change in voltage of the detection signal SD is output from the output node NQ corresponding to the source of the N-type transistor TN.

  Here, when manufacturing the detection circuit of the comparative example on the IC substrate, the following manufacturing variations exist as items that cause variations in the output characteristics of the source follower circuit. For example, there are variations in the current supply capability of the transistor TN, variations in threshold values, variations in shape, variations in sheet resistance value of the resistor R, variations in the shape of the resistor R, and the like.

  In general, the characteristic variation of the resistance manufactured on the IC substrate varies more than the characteristic variation of the transistor. In addition, the characteristic variation of the resistance depending on the variation of the manufacturing conditions and the characteristic variation of the transistor are not linked. For this reason, the characteristic variation of the output voltage VQ of the detection circuit of the comparative example of FIG. 1 becomes very large.

  For example, FIG. 2 shows a characteristic example of subject temperature-output voltage when the detection circuit of the comparative example is used as an infrared detection circuit. In FIG. 2, the horizontal axis represents the subject temperature, and the vertical axis represents the output voltage VQ of the detection circuit when infrared rays generated from the subject are received. A1, A2, A3, and A4 in FIG. 2 are four plots of output voltage characteristics of the detection circuit when the characteristics of the transistor TN and the resistance R vary within a general IC manufacturing standard.

  Specifically, A1, A2, A3, and A4 in FIG. 2 are examples of subject temperature-output voltage characteristics in cases 1, 2, 3, and 4, respectively. Here, in case 1, the resistance value RV of the resistor R is increased, the gate width W of the transistor TN is increased, the gate length L is decreased, the threshold voltage Vth is decreased, and the gate film thickness FTC is decreased. The case characteristics. Case 2 has characteristics when RV is low, W is small, L is large, Vth is low, and FTC is thin. Case 3 has characteristics when RV is increased, W is increased, L is decreased, Vth is increased, and FTC is increased. Case 4 has characteristics when RV is low, W is small, L is large, Vth is high, and FTC is thick.

  As shown by A1, A2, A3, and A4 in FIG. 2, in the detection circuit of the comparative example, the variation in the output voltage VQ due to the variation in the element characteristics of each detection circuit is more than the subject temperature dependence of the output voltage VQ. Is much bigger. For this reason, there is a problem that the detection accuracy of the detection circuit cannot be maintained.

  In particular, when an FPA (Focal Plane Array) is configured by arranging pyroelectric elements in a matrix, a plurality of detection circuits shown in FIG. 1 are arranged on the IC substrate. The outputs of the detection circuits are bundled through a row selection transistor or the like and connected to an amplifier circuit or an A / D converter. At this time, if the change in the output voltage due to the characteristic variation of each detection circuit is larger than the object temperature dependence of the output voltage of the detection circuit, the signals from the amplification circuits are bundled by combining the outputs of the plurality of detection circuits. It becomes difficult to amplify or convert the output voltage to digital data by an A / D converter. That is, when a plurality of detection circuits are connected to a single amplifier circuit or A / D converter, the amplifier circuit or A / D converter is stable with respect to all the detection circuits whose output voltage characteristics vary. It is very difficult to design to work. In addition, it is extremely difficult to determine the intensity of infrared rays applied to each pyroelectric element 10 and the temperature of the subject that has emitted the infrared rays.

  In addition, in order for the source follower circuit including the transistor TN and the resistor R in FIG. 1 to operate, the transistor TN needs to be stably turned on. The gate voltage of the transistor TN is approximately 0V. Therefore, in order to turn on the transistor TN, it is necessary to design the source voltage of the transistor TN, that is, the output voltage VQ of the detection circuit, to be a voltage sufficiently lower than the absolute value of the threshold value of the transistor TN.

  On the other hand, when a sensor array is formed on an IC substrate, an amplifier circuit and an A / D converter that receive the output of the detection circuit are connected to a GND terminal having the same potential as the GND terminal of the detection circuit in a CMOS process. The circuit will be designed. In this case, when the input voltage of these circuits approaches 0V (= GND terminal potential), problems such as a reduction in circuit capability or a failure of operation occur.

2. Configuration and Operation of Detection Circuit FIG. 3 shows a configuration example of the detection circuit of this embodiment that solves the above problems. This detection circuit has a pixel circuit 20 including a pyroelectric element 10 and a source follower circuit 12. The source follower circuit 12 includes a first P-type transistor TP1 and a second P-type transistor TP2 provided in series between the high potential power supply VCC and the low potential power supply GND. The source follower circuit 15 outputs a voltage having an amplitude with a gain of approximately 0.5 as the output voltage VQ with respect to a small signal amplitude change of the detection signal SD.

  The equivalent circuit of the pyroelectric element 10 (heat detection element, infrared detection element, sensor element) is configured by a capacitance CP and a resistance RP, and the pyroelectric body 11 of the pyroelectric element 10 is subject to a change in temperature due to incidence of infrared rays. Corresponding spontaneous polarization has occurred.

  The first P-type transistor TP1 (P-type MOS transistor) is provided between the output node NQ and the GND node (low potential power supply node) of the detection circuit. For example, in FIG. 3, the source of TP1 is connected to the output node NQ, the drain is connected to the GND node, and the detection signal SD from the pyroelectric element 10 is input to the gate.

  The second P-type transistor TP2 (P-type MOS transistor) is provided between the VCC node (high potential power supply node) and the output node NQ. For example, in FIG. 3, the source of TP2 is connected to the VCC node, the drain is connected to the output node NQ, the gate is connected to the output node NQ, and the gate is set to the reference voltage Vcc / 2. Here, Vcc represents the voltage of the high potential power supply VCC.

  Note that another circuit element (for example, a row selection transistor) may be provided between the P-type transistors TP1 and TP2.

  Further, the substrate potential of the P-type transistor TP1 is set to the potential of the source of TP1. For example, in FIG. 3, the substrate potential of TP1 is connected to the output node NQ. The substrate potential of the P-type transistor TP2 is set to the potential of the source of TP2. For example, in FIG. 3, the substrate potential of TP2 is connected to the VCC node. Since the substrate potentials of the P-type transistors TP1 and TP2 are set to their source potentials in this way, fluctuations in the threshold voltages of TP1 and TP2 due to the substrate bias effect can be prevented. , Can be closer. It is also possible to perform a modification in which the substrate potentials of the P-type transistors TP1 and TP2 are both set to the VCC potential.

  The P-type transistors TP1 and TP2 have the same gate length and / or gate width. More preferably, TP1 and TP2 have the same gate length and gate width. In this way, it is possible to make the device characteristics such as the threshold voltages of the P-type transistors TP1 and TP2 close to each other, and the fluctuation of the output voltage VQ due to the manufacturing process fluctuation or the like can be suppressed.

  In addition, as will be described later, it is desirable that the P-type transistors TP1 and TP2 are arranged adjacent to each other. In this way, variations in element characteristics such as threshold voltages of the P-type transistors TP1 and TP2 can be reduced, so that variations in the output voltage VQ can be further reduced.

  Note that the layout arrangement adjacently means that TP1 and TP2 are arranged without any other circuit elements (transistors, resistors, etc.) arranged therebetween. Further, the first P-type transistor TP1 may be disposed adjacent to the first P-type transistor included in the detection circuit of another pyroelectric element. Similarly, the second P-type transistor TP2 may be disposed adjacent to a second P-type transistor included in another pyroelectric element detection circuit.

  Further, as will be described later, the P-type transistor TP2 may be shared with other pyroelectric element detection circuits. That is, the P-type transistor TP2 may be shared as a common current source for a plurality of detection circuits. By doing so, it is possible to minimize the layout occupation area of the second P-type transistor.

  Next, the operation of the detection circuit of this embodiment will be described in more detail. As shown in FIG. 3, the gate of the transistor TP2 is connected to the output node ND and is set to substantially the reference voltage Vcc / 2. Accordingly, since the gate-source voltage of the transistor TP2 is almost Vcc / 2 and TP2 operates in the saturation region, the current I1 almost determined only by the gate-source voltage Vcc / 2 and the threshold voltage is present in TP2. Flowing.

  On the other hand, since the transistor TP1 is connected in series to the transistor TP2, the same current I1 flows through TP1. The substrate potential of the transistor TP1 is set to the source potential similarly to the transistor TP2. Therefore, the threshold voltage of the transistor TP1 and the threshold voltage of the transistor TP2 can be made equal. Further, if the transistor TP1 operates in a saturation region and the transistors TP1 and TP2 have the same transistor size (the same gate width and gate length), the gate-source voltage of TP1 is the gate-source voltage of TP2. The voltage is almost the same as a certain Vcc / 2. In addition, since the gate of the transistor TP1 is connected to the pyroelectric element 10, and the resistance RP of the pyroelectric element 10 exists between the node ND and GND of the gate of TP1, the node ND is constantly set to 0V. The Therefore, the voltage VQ of the output node NQ of the detection circuit, which is the source node of the transistor TP1, is constantly set to substantially the same voltage as Vcc / 2.

  In this state, when the pyroelectric element 10 is irradiated with infrared rays and the temperature of the pyroelectric element 10 changes, the gate (gate capacitance) of the transistor TP1 is transiently charged by the generated pyroelectric current, and the voltage fluctuates by ΔV. At this time, since equal currents flow through the transistors TP1 and TP2, the voltage at the node NQ changes so that the gate-source voltages of the transistors TP1 and TP2 become equal. As a result, the gate-source voltages of the transistors TP1 and TP2 are both Vcc / 2−ΔV / 2. At this time, VQ which is the source voltage of TP1 is VQ = Vcc / 2 + ΔV / 2. That is, the circuit composed of the transistors TP1 and TP2 operates as a source follower circuit with a gain = 0.5.

This is also clear from the following equation. The current I1 flowing through the first and second P-type transistors TP1 and TP2 is
_{I1 = β TP2 (Vcc-VQ-} | Vth TP2 |) 2/2 = β TP1 (VQ-SD- | Vth TP1 |) 2/2
It becomes.

Here, if the sizes of the first and second P-type transistors TP1 and TP2 are made equal,
β _TP2 = β _TP1 , Vth _TP2 = Vth _TP1
Than,
VQ = (V _cc + SD) / 2
Thus, the output VQ is a value that does not depend on transistor characteristics, that is, process variation.

  As described above, in this embodiment, when Vcc is supplied as the high potential power supply voltage, the gate of the P-type transistor TP2 connected to the output node NQ is set to the reference voltage Vcc / 2. The P-type transistor TP1 outputs, to the source thereof, a voltage that changes with the voltage change of the detection signal SD from the pyroelectric element 10 with reference to the set voltage corresponding to Vcc / 2. For example, when the temperature of the pyroelectric element 10 changes and the voltage of the detection signal SD changes from 0 V by ΔV, the output voltage VQ also changes by ΔV / 2 with reference to the set voltage corresponding to Vcc / 2.

  Therefore, as shown in FIG. 3, a differential amplifier circuit OP that differentially amplifies the output voltage VQ that is the output of the pixel circuit 20 and the reference voltage Vcc / 2 is provided, and the detection signal is output as the output of the differential amplifier circuit OP. A fluctuation voltage A · ΔV / 2 proportional to SD can be obtained. Here, A is the gain of the differential amplifier circuit OP, and A = C1 / C2. In FIG. 3, the reference voltage Vcc / 2 of the differential amplifier circuit OP is obtained by dividing the power supply voltage Vcc by two resistors R. However, a reference voltage Vcc / 2 from a reference voltage generation circuit described later is used. May be.

  Further, when the threshold voltage of the P-type transistor TP2 (TP1) is Vth, Vth <Vcc / 2 <Vcc is satisfied. That is, the reference voltage Vcc / 2 that satisfies this relationship is input to the gate of the P-type transistor TP2. In this way, the transistors TP1 and TP2 can be operated in the saturation region. In addition, since Vcc / 2, which is the set voltage of the output voltage VQ, is equal to or higher than the threshold voltage Vth, a voltage higher than the threshold voltage Vth is steadily input to the subsequent amplifier circuit and A / D converter. become able to. Therefore, the design of the subsequent stage amplifier circuit and A / D converter can be facilitated, and a compact and simple circuit can be used as the amplifier circuit and A / D converter.

  FIG. 4 shows an example of a hysteresis loop of the ferroelectric pyroelectric element 10. E1 is a hysteresis loop when the temperature is low, and E2 is a hysteresis loop when the temperature is high. As shown in FIG. 4, the spontaneous polarization PR2 (residual polarization) in the hysteresis loop at a high temperature is smaller than the spontaneous polarization PR1 at a low temperature.

  When infrared rays are irradiated and the temperature of the pyroelectric element 10 changes, the spontaneous polarization of the pyroelectric element 10 changes according to the amount of temperature change. At this time, movement of the surface charges of the electrodes 12 and 13 occurs so as to maintain the spontaneous polarization and the electrical neutral state of the pyroelectric element 10, thereby generating a pyroelectric current. Therefore, the magnitude of the pyroelectric current depends on the temperature change amount of the pyroelectric element 10. The gate (gate capacitance) of the transistor TP1 is charged by the generated pyroelectric current, and the ultimate voltage (ΔV) of the detection signal SD of the pyroelectric element 10 changes. Therefore, by outputting this reached voltage as the output voltage VQ via the source follower circuit composed of the transistors TP1 and TP2 in FIG. 3, it becomes possible to detect a change in the temperature of the pyroelectric element 10 due to the irradiation of infrared rays.

  As described above, in the source follower circuit of the infrared detection circuit of the present embodiment, a resistor having a large characteristic variation as in the comparative example of FIG. 1 is not used as a load element. In addition, since the two elements constituting the source follower circuit are both P-type MOS transistors, the characteristic variation of the two elements depending on the variation of the manufacturing conditions is linked, and the characteristic variation of the output voltage VQ of the detection circuit is small. Become.

  The substrate potentials of the transistors TP1 and TP2 are connected to their source terminals. Therefore, since the threshold voltages of the transistors TP1 and TP2 are substantially equal, the variation in characteristics of the output voltage VQ of the detection circuit can be further reduced.

  Further, the transistors TP1 and TP2 are set to the same transistor size (gate length and gate width), and the same current I1 flows through the transistors TP1 and TP2 connected in series, and both operate in the saturation region. In addition, since the transistor sizes are set to be the same, the minute difference in threshold voltage is further reduced. For this reason, these transistors TP1 and TP2 operate in a state in which all parameters other than the source-drain voltage are substantially equal. Therefore, the characteristic variation of the output voltage VQ of the detection circuit is further reduced.

  For example, FIG. 5 shows an example of subject temperature-output voltage characteristics when the detection circuit of the present embodiment is used as an infrared detection circuit. B1, B2, B3, and B4 in FIG. 5 are four plots of output voltage characteristics of the detection circuit when the characteristics of the transistors TP1 and TP2 vary within a general IC manufacturing standard. B1, B2, B3, and B4 in FIG. 5 correspond to cases 1, 2, 3, and 4 of A1, A2, A3, and A4 in FIG.

  As understood from FIG. 5, in the detection circuit of this embodiment, the change in the output voltage due to the characteristic variation of each detection circuit is sufficiently small with respect to the subject temperature dependence of the output voltage. Therefore, circuits such as an amplifier circuit and an A / D converter that use the output of the detection circuit of the present embodiment as an input are more stable than a plurality of connected detection circuits (circuits with different characteristics). It can be designed to work. Therefore, the design can be facilitated, and a compact and simple circuit can be adopted as an amplifier circuit or an A / D converter.

  If the output voltage of the infrared detection circuit can be stably acquired as digital data, the variation in the output voltage of each detection circuit is within a range that can be sufficiently corrected by software. It is possible to determine the intensity of the infrared rays and the temperature of the subject that has emitted the infrared rays with high accuracy.

  Further, since the transistors TP1 and TP2 are laid out adjacent to each other as will be described later, the characteristic variation of the two transistors TP1 and TP2 is further reduced, and the characteristic variation of the output voltage of the detection circuit is further reduced.

  In the detection circuit of Patent Document 1 described above, a source grounding circuit is configured by a P-type transistor and an N-type transistor connected in series. However, in the source ground circuit having such a configuration, the threshold voltages of the P-type transistor and the N-type transistor do not cancel each other, and the output of the detection circuit is caused by the characteristic variation of the P-type transistor and the N-type transistor. The voltage will fluctuate.

  On the other hand, in the detection circuit of this embodiment, the threshold voltages of the P-type transistors TP1 and TP2 are canceled out, and it is possible to suppress the occurrence of characteristic variations such as the threshold voltages as variations in output voltage. . Therefore, as compared with the detection circuit disclosed in Patent Document 1, variations in output voltage can be reduced, and infrared detection accuracy and the like can be improved.

3. Detection Circuit Having Reference Voltage Generation Circuit The detection circuit of the present embodiment is not limited to the configuration shown in FIG. 3, and various modifications can be made. For example, FIG.6 and FIG.7 shows the modification of the detection circuit of this embodiment. In this modification, a reference voltage generation circuit is provided separately from the source follower circuit.

  6 and 7 are different from FIG. 3 in that a reference voltage generating circuit for supplying a reference voltage Vcc / 2 to the gate of the second P-type transistor TP2 instead of connecting the gate to the output node NQ. 30 is provided.

  The reference voltage generation circuit 30 includes a third P-type transistor TP3 and a fourth P-type transistor TP4 connected in series between a high potential power supply node and a low potential power supply node. The connection node NR between the source of the third P-type transistor TP3 whose low-potential power supply node is connected to the drain and the drain of the fourth P-type transistor TP4 whose high-potential power supply node is connected to the source is the reference voltage generation The output node of the circuit 30 is used.

  The third P-type transistor TP3 has a low power supply node connected to the gate, and the fourth P-type transistor TP4 has the output node NR of the reference voltage generation circuit 30 connected to the gate.

  That is, the configuration of the third and fourth P-type transistors TP3 and TP4 of the reference voltage generation circuit 30 is substantially the same as the configuration of the first and second P-type transistors TP1 and TP2 connected to the pyroelectric element 10. It is. This is because the gate of the third P-type transistor TP3 is supplied with the voltage 0V of the low potential power supply node, but the gate voltage SD of the first P-type transistor TP1 is 0V as described above in the steady state of the pyroelectric element 10. .

  Here, the voltage at the output node NR of the reference voltage generating circuit 30 is the same as that of the first and second P-type transistors TP1 and TP2 when the pyroelectric element 10 is in a steady state. When TP4 operates, a constant voltage of Vcc / 2 is obtained. Therefore, the reference voltage Vcc / 2 can be supplied to the gate of the second P-type transistor TP2.

  Thus, the third and fourth P-type transistors TP3 and TP4 of the reference voltage generating circuit 30 are the same as the source follower circuit of the first and second P-type transistors TP1 and TP2 connected to the pyroelectric element 10. Even if there is a process variation, the same tendency as that of the first and second P-type transistors is obtained, so that it is possible to ensure an output with less dependence on process variations. In particular, if the first to fourth P-type transistors have the same size, the influence of process variations can be minimized.

The current I1 flowing through the first and second P-type transistors TP1 and TP2 shown in FIG. 6 has a detection signal voltage of the pyroelectric element 10 as SD.
_{I1 = β TP2 (Vcc / 2-} | Vth TP2 |) 2/2 = β TP1 (VQ-SD- | Vth TP1 |) 2/2
It becomes. If the sizes of the first and second P-type transistors TP1 and TP2 are equal, _βTP1 = _βTP2 , _VthTP1 = Vth _TP2 , VQ = Vcc / 2 + SD, and the source follower circuit 15 gain is 1 and the output is independent of transistor characteristics, that is, process variations.

  FIG. 8 shows an example of subject temperature-output voltage characteristics when the detection circuit of FIG. 6 is employed. FIG. 8 plots the output voltage characteristics of the detection circuit in four ways (cases 1 to 4) when the characteristics of the transistors TP1, TP2, and the like vary within general IC manufacturing standards, as in FIGS. It is a thing.

  If the reference voltage generating circuit 30 as shown in FIG. 6 is provided, the gain of the source follower circuit can be improved from 0.5 to 1 as apparent from a comparison between FIG. 8 and FIG. Detection accuracy such as temperature detection by a circuit can be further improved.

  FIG. 7 differs from FIG. 6 in that the output Vcc / 2 of the reference voltage generation circuit 30 is supplied to the substrate potential of the first P-type transistor TP1.

The current I1 flowing through the first and second P-type transistors TP1 and TP2 shown in FIG.
_{I1 = β TP2 (V CC /} 2- | Vth TP2 |) 2/2 = β TP1 (VQ-SD- | Vth TP1 |) 2/2
Here, if the sizes of the first and second P-type transistors TP1 and TP2 are made equal,
β _TP1 = β _TP2 , Vth _TP1 ≒ Vth _TP2
Than,
VQ = Vcc / 2 + SD- | Vth _TP2 | + | Vth _TP1 | However, Vth _TP1 ≒ Vth _TP2
It becomes.

Here, since | Vth _TP1 |-| Vth _TP2 | substantially cancels out the influence of process variation, VQ is an output that is substantially independent of transistor characteristics, that is, process variation.

  In FIG. 7, the substrate potential of the first P-type transistor TP1 is set to the reference voltage Vcc / 2 of the reference voltage generation circuit 30 in order to reduce the pattern area as compared with FIG.

However, the value of Vth _M1 shifts from Vth _M2 depending on VQ due to the back gate effect.
At this time, the deviation amount | Vth _TP1 | − | Vth _TP2 | is proportional to (Vcc / 2−VQ) ^1/2 , but may be approximated to be proportional to Vcc / 2−VQ in the operation range of this circuit.

For this reason,
VQ ≒ Vcc / 2 + SD + α (Vcc / 2-SD) ≒ Vcc / 2 + SD / (1 + α)
(Where α is a positive proportionality coefficient), and the gain is smaller than in FIG.

4). Sensor Device FIG. 9A shows a configuration example of the sensor device of this embodiment. The sensor device includes a sensor array 100, a row selection circuit (row driver) 110, and a readout circuit 120. An A / D converter 130 and a control circuit 150 can be included. By using this sensor device, for example, an infrared camera used in a night vision device or the like can be realized.

  A plurality of sensor cells are arranged (arranged) in the sensor array 100 (focal plane array). A plurality of row lines (word lines, scanning lines) and a plurality of column lines (data lines) are provided. The number of column lines may be one. When the number of column lines is one, a line sensor in which a plurality of sensor cells are arranged in a direction (vertical direction) along the column line is configured.

  Each sensor cell of the sensor array 100 is arranged (formed) at a location corresponding to the intersection position of each row line and each column line. For example, the sensor cell of FIG. 9B is disposed at a location corresponding to the intersection position of the row line WL1 and the column line DL1. The same applies to other sensor cells.

  The row selection circuit 110 is connected to one or a plurality of row lines. Then, each row line is selected. For example, taking a QVGA (320 × 240 pixel) sensor array 100 (focal plane array) as shown in FIG. 9B as an example, row lines WL0, WL1, WL2,... WL239 are sequentially selected (scanned). Perform the action. That is, a signal (word selection signal) for selecting these row lines is output to the sensor array 100.

  The read circuit 120 is connected to a plurality of column lines. Then, a read operation for each column line is performed. Taking the QVGA sensor array 100 as an example, an operation of reading detection signals (detection current, detection charge) from the column lines DL0, DL1, DL2,. For example, the read circuit 120 is provided with each amplifier circuit corresponding to each column line of a plurality of column lines. Each amplifier circuit amplifies the signal of the corresponding column line.

  The A / D conversion unit 130 performs a process of A / D converting the detection voltage (measurement voltage, ultimate voltage) acquired in the readout circuit 120 into digital data. Then, the digital data DOUT after A / D conversion is output. Specifically, the A / D converter 130 is provided with each A / D converter corresponding to each of the plurality of column lines. Each A / D converter performs A / D conversion processing of the detection voltage acquired by the reading circuit 120 in the corresponding column line. Note that one A / D converter is provided corresponding to a plurality of column lines, and the detection voltage of the plurality of column lines can be A / D converted in a time division manner using this one A / D converter. Good. Further, the signal of each column line may be directly input to each A / D converter of the A / D converter 130 without providing the amplifier circuit of the readout circuit 120.

  The control circuit 150 (timing generation circuit) generates various control signals and outputs them to the row selection circuit 110, the readout circuit 120, and the A / D conversion unit 130. For example, a signal for controlling the timing of each circuit is generated and output.

  FIG. 10 shows a detailed first configuration example of the sensor device of the present embodiment. FIG. 10 mainly shows a detailed configuration of the sensor array 100.

  In FIG. 10, SC00 to SCnm are sensor cells arranged in an array. WL0 to WLm are row lines (row selection lines), and DL0 to DLn are column lines (column data lines). QC0 to QCn are amplifier circuits connected to the column lines DL0 to DLn, and output signals obtained by amplifying the voltages of the column lines DL0 to DLn as DQ0 to DQn. QC0 to QCn may be A / D converters that directly A / D convert the voltages of the column lines DL0 to DLn.

  Each sensor cell of the plurality of sensor cells SC00 to SCnm includes a pyroelectric element 10 and first and second P-type transistors TP1 and TP2. A row selection transistor TS is also included.

  The first P-type transistor TP1 is provided between the output node NQ to the corresponding column line corresponding to each sensor cell and the GND node (low potential power supply node). A detection signal from the pyroelectric element 10 is input to the gate of TP1.

  The second P-type transistor TP2 is provided between the VCC node (high potential power supply node) and the output node NQ. The gate of TP2 is set to the reference voltage Vcc / 2. The reference voltage Vcc / 2 is generated by the reference voltage generation circuit 30 and supplied to the sensor cells SC00 to SCnm.

  The row selection transistor TS is provided between the output node NQ and the corresponding column line of each sensor cell. The corresponding row line corresponding to each sensor cell is connected to the gate of TS. Each sensor cell of the plurality of sensor cells provided corresponding to the corresponding column line is connected to the corresponding column line via the row selection transistor TS. That is, the row selection transistor TS of each sensor cell is connected to the corresponding row line corresponding to the sensor cell among the row lines WL0 to WLm. Then, when the corresponding row line becomes H level, for example, the row selection transistor TS is turned on, and the output node NQ of the sensor cell and the corresponding column line of the sensor cell are connected.

  For example, sensor cells SC00 to SC0m are connected to corresponding column line DL0 of SC00 to SC0m. Specifically, the output node NQ of each sensor cell of SC00 to SC0m is connected to the corresponding column line DL0 via the row selection transistor TS. Similarly, sensor cells SC10 to SC1m are connected to corresponding column line DL1 of SC10 to SC1m. Specifically, the output node NQ of each sensor cell of SC10 to SC1m is connected to the corresponding column line DL1 via the row selection transistor TS. The same applies to the other sensor cells SCn0 to SCnm.

  The row selection transistors TS of the sensor cells SC00, SC10... SCn0 provided corresponding to the row line WL0 are turned on when the row line WL0 becomes H level. Then, output nodes NQ of sensor cells SC00, SC10... SCn0 are connected to the corresponding column lines DL0, DL1. As a result, signals from the sensor cells SC00, SC10... SCn0 are read out and output to the corresponding column lines DL0, DL1... DLn, and can be configured by the differential amplifier circuit OP shown in FIG. Amplified by QCn and output as signals DQ0 to DQn.

  Further, the row selection transistors TS of the sensor cells SC01, SC11... SCn1 provided corresponding to the row line WL1 are turned on when the row line WL1 becomes H level. Thereby, output nodes NQ of sensor cells SC01, SC11... SCn1 are connected to corresponding column lines DL0, DL1. As a result, signals from the sensor cells SC01, SC11,..., SCn1, are read out and output to the corresponding column lines DL0, DL1,. Is done. The operation of sensor cells connected to other row lines WLm and the like is the same.

  According to the first configuration example of FIG. 10, since two P-type transistors TP1 and TP2 are provided for each sensor cell, the area occupied by the transistors in each sensor cell increases. However, for example, a transistor is formed below the pyroelectric element 10 formed of a ferroelectric film or the like, and the occupied area of the pyroelectric element 10 may be larger than the occupied area of the transistor. In such a case, even if the P-type transistors TP1 and TP2 are provided in each sensor cell as shown in FIG.

  On the other hand, according to the method of providing the P-type transistors TP1 and TP2 in each sensor cell as shown in FIG. 10, the manufacturing conditions of the P-type transistors TP1 and TP2 can be made uniform. The circuit characteristics can be made substantially the same, and there is an advantage that variation in output voltage can be further reduced.

  FIG. 11 shows a detailed second configuration example of the sensor device of the present embodiment. The second configuration example in FIG. 11 is different from the first configuration example in FIG. 10 in the configuration of the sensor cell. In FIG. 11, a current source circuit 40 connected to the column lines DL0 to DLn is further provided.

  Each sensor cell of SC00 to SCnm includes a pyroelectric element 10 and a first P-type transistor TP1. The first P-type transistor TP1 is provided between the output node NQ and the GND node to the corresponding column line corresponding to each sensor cell, and the detection signal from the pyroelectric element 10 is input to the gate.

  Each sensor cell of SC00 to SCnm includes a row selection transistor TS. The row selection transistor TS is provided between the output node NQ and the corresponding column line of each sensor cell. The corresponding row line corresponding to each sensor cell is connected to the gate of TS. That is, the row selection transistor TS of each sensor cell is connected to the corresponding row line corresponding to the sensor cell among the row lines WL0 to WLm. Then, when the corresponding row line becomes H level, for example, the row selection transistor TS is turned on, and the output node NQ of the sensor cell and the corresponding column line of the sensor cell are connected.

  The current source circuit 40 includes second P-type transistors TPC0 to TPCn. The second P-type transistors TPC0 to TPCn correspond to the second P-type transistor TP2 of FIG. That is, in FIG. 11, the P-type transistors TPC0 to TPCn are shared as the second P-type transistors of the sensor cells connected to the corresponding column lines, and the P-type transistors TPC0 to TPCn of the current source circuit 40 are used. And a P-type transistor TP1 of the sensor cell constitute a source follower circuit.

  In FIG. 11, the current source circuit 40 is provided with a plurality of P-type transistors TPC0 to TPCn. In the case of a line sensor having one column line, the current source circuit 40 is connected to the one column line. One second P-type transistor may be provided.

  Each P-type transistor of TPC0 to TPCn is provided between the VCC node and the corresponding column line. The gate is set to the reference voltage Vcc / 2, and current (constant current) is supplied to each sensor cell of SC00 to SCnm via the corresponding column line. For example, the P-type transistor TPC0 is provided between the VCC node and the corresponding column line DL0, and supplies current to the sensor cells SC00 to SC0m of the corresponding column line DL0. P-type transistor TPC1 is provided between the VCC node and corresponding column line DL1, and supplies current to sensor cells SC10 to SC1m of corresponding column line DL1. The same applies to other P-type transistors TPCn and the like.

  For example, the row selection transistors TS of the sensor cells SC00, SC10... SCn0 provided corresponding to the row line WL0 are turned on when the row line WL0 becomes H level. Then, output nodes NQ of sensor cells SC00, SC10... SCn0 are connected to the corresponding column lines DL0, DL1. Thereby, the constant current from the P-type transistors TPC0 to TPCn of the current source circuit 40 flows to the P-type transistors TP1 of the sensor cells SC00, SC10... SCn0, and the same operation as that of the detection circuit of FIG. Then, signals from the sensor cells SC00, SC10... SCn0 are read out and output to the corresponding column lines DL0, DL1... DLn, amplified by the amplifier circuits QC0 to QCn, and output as signals DQ0 to DQn. Is done. The operation of the sensor cells SC01 to SCnm connected to the row lines WL1 to WLm is the same.

  According to the second configuration example of FIG. 11, the second P-type transistors TPC0 to TPCn are shared by a plurality of detection circuits. Therefore, since only one P-type transistor TP1 needs to be provided for each sensor cell, the area occupied by the transistors in each sensor cell can be reduced compared to the first configuration example of FIG. However, the P-type transistor TP1 and TPC0 to TPCn are laid out at positions distant from each other as compared with the first configuration example of FIG. For this reason, the manufacturing conditions and the like of the P-type transistor TP1 and TPC0 to TPCn vary, and the variation in output voltage may increase compared to the first configuration example of FIG.

5. Electronic Device FIG. 12 shows a configuration example of an electronic device including the sensor device and detection circuit of this embodiment. The electronic apparatus includes an optical system 200, a sensor device 210 (detection circuit), an image processing unit 220, a processing unit 230, a storage unit 240, an operation unit 250, and a display unit 260. Note that the electronic apparatus of the present embodiment is not limited to the configuration shown in FIG. 14, and some of the components (for example, an optical system, an operation unit, a display unit, etc.) are omitted, or other components are added. Various modifications of the above are possible.

  The optical system 200 includes, for example, one or a plurality of lenses and a driving unit that drives these lenses. Then, an object image is formed on the sensor device 210. If necessary, focus adjustment is also performed.

  The sensor device 210 has been described with reference to FIGS. 9A to 11 and the like, and performs an object image capturing process. The image processing unit 220 performs various image processing such as image correction processing based on digital image data (pixel data) from the sensor device 210. Instead of the sensor device 210 serving as an image sensor, the detection circuit described with reference to FIGS. 3 and 6 to 7 may be used.

  The processing unit 230 controls the entire electronic device or controls each block in the electronic device. The processing unit 230 is realized by a CPU or the like, for example. The storage unit 240 stores various types of information, and functions as a work area for the processing unit 230 and the image processing unit 220, for example. The operation unit 250 is an interface for a user to operate an electronic device, and is realized by various buttons, a GUI (Graphical User Interface) screen, and the like. The display unit 260 displays, for example, an image acquired by the sensor device 210 or a GUI screen, and is realized by various displays such as a liquid crystal display and an organic EL display, a projection display device, and the like.

  The present embodiment can be applied to an infrared camera using an FPA (Focal Plane Array) and an electronic device using the infrared camera. Electronic devices to which infrared cameras are applied include, for example, night vision devices that capture night-time object images, thermographic devices that acquire the temperature distribution of objects, intrusion detection devices that detect human intrusions, and analysis (measurement of physical information on objects) Analysis equipment (measuring equipment), security equipment that detects fire and heat generation, FA (Factory Automation) equipment installed in factories, etc. can be assumed. If a night vision device is applied to an in-vehicle device, it is possible to detect and display the appearance of a person at night when the vehicle is running. If applied to a thermographic device, it can be used for influenza quarantine.

  FIG. 13 shows an example of an electronic apparatus including the pyroelectric detector or the pyroelectric detector according to the present embodiment. An example in which the specific substance detection apparatus 1000 is configured using the sensor device described above as a terahertz light sensor device in combination with a terahertz light irradiation unit.

  The specific substance detection apparatus 1000 includes a control unit 1010, an irradiation light unit 1020, an optical filter 1030, an imaging unit 1040, and a display unit 1050. The imaging unit 1040 includes an optical system such as a lens (not shown) and a sensor device in which the absorption wavelength of the light absorbing material of the pyroelectric detector described above is in the terahertz range.

  The control unit 1010 includes a system controller that controls the entire apparatus, and the system controller controls the light source driving unit and the image processing unit included in the control unit. The irradiation light unit 1020 includes a laser device that emits terahertz light (an electromagnetic wave having a wavelength in the range of 100 μm to 1000 μm) and an optical system, and irradiates the person 1060 to be inspected with terahertz light. The reflected terahertz light from the person 1060 is received by the imaging unit 1040 through the optical filter 1030 that allows only the spectral spectrum of the specific substance 1070 to be detected to pass. The image signal generated by the imaging unit 1040 is subjected to predetermined image processing by the image processing unit of the control unit 1010, and the image signal is output to the display unit 1050. The presence of the specific substance 1070 can be determined because the intensity of the received light signal varies depending on whether or not the specific substance 1070 is present in the clothes of the person 1060.

  FIG. 14 shows a terahertz camera 1100 that receives and images light having a frequency of terahertz. The terahertz camera 1100 includes a slit 1120 and a lens 1130 in a housing 1110.

  As shown in FIG. 15, a terahertz light source 1200 and a light source driving circuit 1210 are provided in the housing 1110, and emits terahertz light toward an object through a slit 1120.

  The reflected light from the object is collected by the lens 1130 and detected by the sensor device (pyroelectric detection device) 1220 according to the above-described embodiment. A digital signal from the sensor device 1220 is subjected to arithmetic processing by the arithmetic processing device 1230, drawn by the drawing processing circuit 1240, stored in the storage device 1250, or displayed on the display device 1260.

  Applications of the terahertz camera are various, and in fields other than those described above, for example, in the field of drug inspection, the pharmaceutical is inspected for the inclusion of the final dosage polymorph, the bias of the medicinal component, the presence of cavities or foreign substances. At the time of dispensing, the type and amount of medicine and foreign matter mixing are inspected. At the time of medication, it is checked whether the type and components of the medication to be administered are correct. In addition, if terahertz cameras are incorporated into various factory lines, it will be possible to check the total number of products.

  Although the present embodiment has been described in detail as described above, it will be easily understood by those skilled in the art that many modifications can be made without departing from the novel matters and effects of the present invention. . Accordingly, all such modifications are intended to be included in the scope of the present invention. For example, in the specification or drawings, terms (VCC node, GND node) described together with different terms (high potential power supply node, low potential power supply node, etc.) in a broader sense or the same meaning at least once It can also be replaced with the different terminology. Further, the configurations and operations of the detection circuit, sensor device, and electronic device are not limited to those described in this embodiment, and various modifications can be made.

TP1 first P-type transistor,
TP2, TPC0 to TPCn Second P-type transistor,
TP3 Third P-type transistor,
TP4 Fourth P-type transistor,
CP capacity, RP, R resistance, SD detection signal, VQ output voltage,
ND detection signal node, NQ detection circuit output node,
NR reference voltage generation circuit output node, WL0 to WLm row lines,
DL0 to DLn column lines,
10 pyroelectric elements, 15 source follower circuit, 20 pixel circuit,
30 reference voltage generation circuit, 40 current source circuit,
100 sensor array, 110 row selection circuit, 120 readout circuit,
130 A / D converter, 150 control circuit

Claims (16)

A pyroelectric element;
A first P-type transistor provided between an output node of the detection circuit and a low-potential power supply node, wherein a detection signal from the pyroelectric element is input to a gate;
A second P-type transistor provided between a high-potential power supply node and the output node and having a gate set to a reference voltage;
Have
2. A detection circuit according to claim 1, wherein the reference voltage is set to Vcc / 2 when the voltage of the high potential power supply node is Vcc and the voltage of the low potential power supply node is GND. In claim 1,
A detection circuit further comprising a differential amplifier circuit for differentially amplifying the voltage of the output node and the reference voltage Vcc / 2. In claim 1 or 2,
A detection circuit, wherein the output node is connected to a gate of the second P-type transistor. In claim 1 or 2,
A reference voltage generating circuit for generating the reference voltage;
The reference voltage generation circuit includes a third P-type transistor and a fourth P-type transistor connected in series between the high-potential power supply node and the low-potential power supply node,
A connection node between the source of the third P-type transistor with the low-potential power supply node connected to the drain and the drain of the fourth P-type transistor with the high-potential power supply node connected to the source is the reference The output node of the voltage generator circuit,
In the third P-type transistor, the low power supply node is connected to a gate,
In the fourth P-type transistor, an output node of the reference voltage generation circuit is connected to a gate. A pyroelectric element;
A first P-type transistor provided between an output node of the detection circuit and a low-potential power supply node, wherein a detection signal from the pyroelectric element is input to a gate;
A second P-type transistor provided between a high-potential power supply node and the output node and having a gate set to a reference voltage;
A reference voltage generating circuit for generating the reference voltage;
Have
The reference voltage generation circuit includes a third P-type transistor and a fourth P-type transistor connected in series between the high-potential power supply node and the low-potential power supply node,
A connection node between the source of the third P-type transistor with the low-potential power supply node connected to the drain and the drain of the fourth P-type transistor with the high-potential power supply node connected to the source is the reference The output node of the voltage generator circuit,
In the third P-type transistor, the low power supply node is connected to a gate,
In the fourth P-type transistor, an output node of the reference voltage generation circuit is connected to a gate. In claim 4 or 5,
The substrate potential of the first P-type transistor is set to the source potential of the first P-type transistor,
A detection circuit, wherein a substrate potential of the second P-type transistor is set to a source potential of the second P-type transistor. In claim 4 or 5,
The substrate potential of the first P-type transistor is set to the potential of the output node of the reference voltage generation circuit,
A detection circuit, wherein a substrate potential of the second P-type transistor is set to a source potential of the second P-type transistor. In any of claims 4 to 7,
2. The detection circuit according to claim 1, wherein the reference voltage generation circuit is shared with a detection circuit of another pyroelectric element. A pyroelectric element;
A first P-type transistor and a second P-type transistor connected in series between a high potential power supply node and a low potential power supply node;
A detection circuit comprising:
A connection node between the source of the first P-type transistor with the low-potential power supply node connected to the drain and the drain of the second P-type transistor with the high-potential power supply node connected to the source is the detection The output node of the circuit,
In the first P-type transistor, a detection signal from the pyroelectric element is input to a gate,
In the detection circuit, the second P-type transistor has an output node of the detection circuit connected to a gate. In claim 9,
The substrate potential of the first P-type transistor is set to the source potential of the first P-type transistor,
A detection circuit, wherein a substrate potential of the second P-type transistor is set to a source potential of the second P-type transistor.   A sensor device comprising the detection circuit according to claim 1. A sensor array in which a plurality of sensor cells are arranged;
Multiple row lines,
One or more column lines;
A row selection circuit connected to the plurality of row lines;
A readout circuit connected to the one or more column lines;
Including
Each sensor cell of the plurality of sensor cells is
A pyroelectric element;
A first P-type transistor provided between an output node to a corresponding column line corresponding to each sensor cell and a low-potential power supply node, and a detection signal from the pyroelectric element is input to a gate;
A second P-type transistor provided between a high-potential power supply node and the output node and having a gate set to a reference voltage;
Including
The sensor device according to claim 1, wherein the reference voltage is set to Vcc / 2 when the voltage of the high potential power supply node is Vcc and the voltage of the low potential power supply node is GND. A sensor array in which a plurality of sensor cells are arranged;
Multiple row lines,
One or more column lines;
A row selection circuit connected to the plurality of row lines;
A readout circuit connected to the one or more column lines;
A current source circuit connected to the one or more column lines;
Including
Each sensor cell of the plurality of sensor cells is
A pyroelectric element;
A first P-type transistor provided between an output node to a corresponding column line corresponding to each sensor cell and a low-potential power supply node, and a detection signal from the pyroelectric element is input to a gate;
The current source circuit is:
A second P-type transistor provided between a high potential power supply node and the corresponding column line, having a gate set to a reference voltage, and supplying a current to each sensor cell via the corresponding column line;
The sensor device according to claim 1, wherein the reference voltage is set to Vcc / 2 when the voltage of the high potential power supply node is Vcc and the voltage of the low potential power supply node is GND. In claim 12 or 13,
Each sensor cell includes a row selection transistor provided between the output node and the corresponding column line, and a corresponding row line corresponding to each sensor cell is connected to a gate;
Each sensor cell of a plurality of sensor cells provided corresponding to the corresponding column line is connected to the corresponding column line via the row selection transistor.   An electronic device comprising the detection circuit according to claim 1.   An electronic device comprising the sensor device according to claim 11.

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