Light Sensor

Abstract

Provided is a light sensor that does not require an external power supply. The light sensor includes: a first light detection unit including a photodiode and having a first wavelength sensitivity characteristic; a first resistor having one end connected to the cathode of the photodiode of the first light detection unit and the other end connected to a ground point; a second light detection unit including a photodiode having an anode connected to the anode of the photodiode of the first light detection unit and having a second wavelength sensitivity characteristic different from the first wavelength sensitivity characteristic; a second resistor having one end connected to the cathode of the photodiode of the second light detection unit and the other end connected to the ground point; and an amplifier circuit having a first input terminal connected to the photodiode of the first light detection unit, a second input terminal connected to the photodiode of the second light detection unit, and an output terminal that outputs a potential based on the potentials of the first input terminal and the second input terminal, and using the power generated by the electromotive force of the first light detection unit and the second light detection unit as an operating power supply.

Description

Technical Field

[0001] The present invention relates to light sensors. Background Art

[0002] Conventionally, there is known a technique related to a photosensor that outputs a signal corresponding to light received by a photodiode from an output circuit (for example, see Patent Document 1).

[0003] [Prior art literature]

[0004] [Patent Literature]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2013-197243. Summary of the invention

[0006] [Problems to be solved by the invention]

[0007] In the conventional optical sensor as described above, the power for driving the output circuit is supplied from the outside of the optical sensor. That is, in the conventional optical sensor, there is a problem that an external power supply for driving the optical sensor must be prepared.

[0008] The present invention has been conceived in view of such a situation, and an object of the present invention is to provide a photosensor that does not require an external power supply.

[0009]

Solutions to Solve the Problem

[0010] A light sensor according to one embodiment of the present invention comprises: a first light detection unit including a photodiode and having a first wavelength sensitivity characteristic; a first resistor having one end connected to the cathode of the photodiode of the first light detection unit and the other end connected to a ground point; a second light detection unit including a photodiode having an anode connected to the anode of the photodiode of the first light detection unit and having a second wavelength sensitivity characteristic different from the first wavelength sensitivity characteristic; a second resistor having one end connected to the cathode of the photodiode of the second light detection unit and the other end connected to the ground point; and an amplifier circuit including a first input terminal connected to the cathode of the photodiode of the first light detection unit, a second input terminal connected to the cathode of the photodiode of the second light detection unit, and an output terminal outputting a potential based on a difference between a potential of the first input terminal and a potential of the second input terminal, and using power generated by the electromotive force of the photodiode of the first light detection unit and the photodiode of the second light detection unit as an operating power supply.

[0011] [Effects of the invention]

[0012] According to the present invention, it is possible to provide a light sensor that does not require an external power source. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 This is a diagram showing an example of the structure of the optical sensor in the first embodiment.

[0014] Figure 2 It is a diagram showing an example of the configuration of the amplifier circuit in the first embodiment.

[0015] Figure 3 It is a diagram showing a first modified example of the configuration of the amplifier circuit in the first embodiment.

[0016] Figure 4 This is a diagram showing an example of the structure of the optical sensor in the second embodiment.

[0017] Figure 5 This is a diagram showing an example of the structure of a photosensor in the third embodiment.

[0018] Figure 6 It is a diagram showing an example of the configuration of an amplifier circuit in the third embodiment.

[0019] Figure 7 It is a diagram showing a first modified example of the configuration of the amplifier circuit in the third embodiment.

[0020] Figure 8 It is a diagram showing a second modified example of the configuration of the amplifier circuit in the third embodiment.

[0021] Fig. 9 It is a diagram showing a second modified example of the configuration of the amplifier circuit in the first embodiment.

[0022] Fig.10 It is a diagram showing a third modified example of the configuration of the amplifier circuit in the first embodiment. DETAILED DESCRIPTION

[0023] [First embodiment]

[0024] Hereinafter, a first embodiment of the present invention will be described with reference to the drawings.

[0025] Figure 1 1 is a diagram showing an example of the structure of the optical sensor 50 according to the first embodiment. The optical sensor 50 includes: a first light detection unit 10; a second light detection unit 20; a first resistor 103; a second resistor 104; a booster circuit 105; an amplifier circuit 406; and an output pin 408.

[0026] In the following description, light refers to electromagnetic waves of a wavelength detectable by the optical sensor 50 , and broadly includes infrared light, ultraviolet light, and the like in addition to visible light.

[0027] The first light detection unit 10 includes a first photodiode 101 .

[0028] The second light detection unit 20 includes a second photodiode 102 .

[0029] The anode of the first photodiode 101 and the anode of the second photodiode 102 are connected to each other at the connection point P4. That is, the second photodiode 102 includes an anode connected to the anode of the first photodiode 101.

[0030] In addition, in the present embodiment, the first light detection unit 10 and the second light detection unit 20 only need to have an element that generates electricity using incident light. As an example, the photodiodes provided in the first light detection unit 10 and the second light detection unit 20 are elements that generate photocurrent by forming a pn junction with an n-type semiconductor and a photovoltaic effect. For example, a photodiode is an element that uses a pn junction like a solar cell.

[0031] One end of the first resistor 103 is connected to the cathode of the first photodiode 101 of the first light detection unit 10 at a connection point P2, and the other end is grounded at a connection point P1.

[0032] One end of the second resistor 104 is connected to the cathode of the second photodiode 102 of the second light detection unit 20 at a connection point P3 , and the other end is grounded at a connection point P1 .

[0033] The first resistor 103 and the second resistor 104 have the same resistance value and temperature characteristics. For example, the resistance value of the first resistor 103 and the resistance value of the second resistor 104 are both 30 kΩ (kilo-ohm).

[0034] The booster circuit 105 includes an input terminal 108 and an output terminal 109. The input terminal 108 is connected to the anode of the first photodiode 101 and the anode of the second photodiode 102 at a connection point P4. The booster circuit 105 boosts the voltage supplied to the input terminal 108 and outputs the voltage to the output terminal 109.

[0035] In this embodiment, the booster circuit 105 is a charge pump type boost DC-DC converter circuit including a clock generation circuit (not shown). In this example, the booster circuit 105 performs a boost operation without using an external power supply.

[0036] The amplifier circuit 406 includes a power supply terminal TP, a power supply terminal TG, a first input terminal TI, a second input terminal TN, and an output terminal TO. The power supply terminal TP is connected to the output terminal 109 of the booster circuit 105. The power supply terminal TG is grounded. The amplifier circuit 406 operates using the power output from the booster circuit 105 as a power supply.

[0037] The first input terminal TI is connected to the cathode of the first photodiode 101 of the first light detection unit 10 at the connection point P2. The second input terminal TN is connected to the cathode of the second photodiode 102 of the second light detection unit 20 at the connection point P3. The output terminal TO is connected to the output pin 408, and outputs a potential based on the potential of the first input terminal and the potential of the second input terminal.

[0038] In this example, the amplifier circuit 406 is a differential amplifier circuit. The first input terminal TI is an inverting input terminal of the amplifier circuit 406. The second input terminal TN is a non-inverting input terminal of the amplifier circuit 406. The output terminal TO outputs a voltage or current based on the potential of the first input terminal TI and the potential of the second input terminal TN. As an example, the output terminal TO outputs the potential of the difference between the potential of the first input terminal TI and the potential of the second input terminal TN.

[0039] [Operation Example of the Optical Sensor 50]

[0040] The first photodiode 101 and the second photodiode 102 both generate electromotive force due to the photovoltaic effect when light is incident. The first photodiode 101 generates a photocurrent I1 flowing from the cathode to the anode of the first photodiode 101 due to the electromotive force. The second photodiode 102 generates a photocurrent I2 flowing from the cathode to the anode of the second photodiode 102 due to the electromotive force.

[0041] The first light detection unit 10 and the second light detection unit 20 have different wavelength sensitivity characteristics. The wavelength sensitivity characteristic refers to the light receiving sensitivity of the light detection unit to the wavelength of incident light.

[0042] The first light detection unit 10 has a first wavelength sensitivity characteristic. The first light detection unit 10 outputs a photocurrent I1 according to the intensity of light incident on the first photodiode 101 and the first wavelength sensitivity characteristic. That is, the first light detection unit 10 includes the first photodiode 101 and has the first wavelength sensitivity characteristic.

[0043] The second light detection unit 20 has a structure that exhibits a power generation characteristic that the power generation amount decreases in a specific wavelength range or a structure that has a filter that exhibits the above power generation characteristic installed relative to the first light detection unit 10. In the following description, the wavelength range in which the power generation amount of the second light detection unit 20 decreases is referred to as the "specific wavelength range".

[0044] In this example, the second light detection unit 20 is provided with a wavelength filter not shown. The second light detection unit 20 detects light that passes through the wavelength filter and enters the second photodiode 102. The wavelength filter has a wavelength characteristic that reduces the sensitivity of a specific wavelength range with respect to the above-mentioned first wavelength sensitivity characteristic. That is, the second light detection unit 20 is provided with the second photodiode 102 and the wavelength filter, and thus has a second wavelength sensitivity characteristic different from the first wavelength sensitivity characteristic as a whole.

[0045] The second wavelength sensitivity characteristic reduces the sensitivity in a specific wavelength range among the wavelength range in which the first wavelength sensitivity characteristic has sensitivity.

[0046] In addition, in the present embodiment, the second light detection unit 20 is provided with a wavelength filter not shown in the figure, and thus is described as a wavelength filter having a second wavelength sensitivity characteristic different from the first wavelength sensitivity characteristic, but the second light detection unit 20 only needs to have a second wavelength sensitivity characteristic different from the first wavelength sensitivity characteristic, and is not limited to this embodiment. For example, the wavelength sensitivity characteristic of the second photodiode 102 included in the second light detection unit 20 may be different from the wavelength sensitivity characteristic of the first photodiode 101.

[0047] When light including a specific wavelength range enters the first light detection section 10 and the second light detection section 20 , the amount of power generated by the second light detection section 20 decreases in proportion to the intensity of light in the specific wavelength range compared to the first light detection section 10 .

[0048] The first resistor 103 and the second resistor 104 have equal resistance values. Photocurrent I1 from the connection point P1 flows into the first resistor 103. Photocurrent I2 from the connection point P1 flows into the second resistor 104. Therefore, in this embodiment, the potential of the connection point P2 and the potential of the connection point P3 are lower than the potential of the connection point P1.

[0049] When the first light detection unit 10 and the second light detection unit 20 detect light in a specific wavelength range, the photocurrent I2 becomes smaller because the power generation characteristics of the specific wavelength range of the second light detection unit 20 are low. When the photocurrent I2 becomes smaller, the potential of the connection point P3 becomes higher. Therefore, the potential of the connection point P3 is proportional to the light intensity in the specific wavelength range and is higher than the potential of the connection point P2.

[0050] In this example, light is incident on the first light detection unit 10 and the second light detection unit 20, thereby generating electromotive force in the first light detection unit 10 and the second light detection unit 20. When the generated electromotive force exceeds a predetermined value (for example, 0.4 V), a photocurrent I1 flows in the first light detection unit 10, and a photocurrent I2 flows in the second light detection unit 20. When the photocurrent I1 or the photocurrent I2 flows, a current flows into the boost circuit 105. The photocurrent I1 flows from the first light detection unit 10 through the connection point P4 to the input terminal 108 of the boost circuit 105, and the photocurrent I2 flows from the second light detection unit 20 through the connection point P4 to the input terminal 108 of the boost circuit 105.

[0051] The boost circuit 105 converts the power generated by the first light detection unit 10 and the second light detection unit 20 into a boosted power of a higher voltage, and supplies the power to the amplifier circuit 406 via the output terminal 109 .

[0052] That is, the booster circuit 105 (boosting unit) supplies the power terminal of the amplifier circuit 406 with power obtained by boosting the power generated by the electromotive force of the first light detection unit 10 and the second light detection unit 20 .

[0053] The amplifier circuit 406 uses the electric power generated by the electromotive force of the first photodiode 101 of the first light detection unit 10 and the second photodiode 102 of the second light detection unit 20 as an operating power source.

[0054] The amplifier circuit 406 outputs a voltage or a current based on the difference between the potential at the connection point P2 and the potential at the connection point P3 to the output pin 408 via the output terminal TO.

[0055] Therefore, the optical sensor 50 in the present embodiment outputs a voltage or a current corresponding to the intensity of light in a specific wavelength range from the output pin 408 .

[0056] [Configuration Example of Amplifier Circuit 406]

[0057] Figure 2 1 is a diagram showing an example of the configuration of the amplifier circuit 406 which is the amplifier circuit in the first embodiment.

[0058] The amplifier circuit 406 includes a transistor 403 , a transistor 404 , a transistor 409 , a transistor 410 , a transistor 401 , a transistor 402 , a resistor 413 , a resistor 411 , a constant current source 405 , and a constant current source 407 .

[0059] The transistor 403, the transistor 404, the transistor 409, and the transistor 410 are all p-channel transistors. The transistor 401 and the transistor 402 are both depletion-type n-channel transistors. In addition, a transistor that is not explicitly described as a depletion-type transistor in the following description may be an enhancement-type transistor.

[0060] The constant current source 405 and the constant current source 407 flow currents of the same current value. The current flowing through the constant current source 405 is referred to as current I 47 , the current flowing through the constant current source 407 is set to current I 48 Current I 47 and current I 48 are the same current values.

[0061] In the depletion type n-channel transistor 401, the gate is connected to the first input terminal TI, the source is connected to the power supply terminal TG via the constant current source 405, and the drain is connected to the drain of the transistor 403. In the depletion type n-channel transistor 402, the gate is connected to the second input terminal TN, the source is connected to the power supply terminal TG via the constant current source 407, and the drain is connected to the drain of the transistor 404. The source of the depletion type n-channel transistor 401 and the source of the depletion type n-channel transistor 402 are connected to each other via the resistor 413.

[0062] The transistor 403 has a source connected to the power supply terminal TP, a gate connected to its own drain and the gate of the transistor 404, and a drain connected to the drain of the depletion-type n-channel transistor 401. The transistor 404 has a source connected to the power supply terminal TP, a gate connected to the gate of the transistor 403 and the drain of the transistor 403, and a drain connected to the drain of the depletion-type n-channel transistor 402.

[0063] The transistor 409 has a gate and a drain connected to the drain of the transistor 404 and a source connected to the power supply terminal TP. The transistor 410 has a gate connected to the drain of the transistor 404, a source connected to the power supply terminal TP, a drain connected to the output terminal TO, and connected to the power supply terminal TG via the resistor 411.

[0064] In this example, the transistor 401 and the transistor 402 constituting the differential pair transistor are both depletion-type n-channel transistors, and thus can cope with an input voltage lower than the power supply terminal TG.

[0065] Here, when the first light detection unit 10 and the second light detection unit 20 detect light in a specific wavelength range, the potential of the second input terminal TN is proportional to the intensity of the light in the specific wavelength range and becomes higher than the potential of the first input terminal TI. The potential difference between the first input terminal TI and the second input terminal TN is substantially equal to the potential difference applied to the resistor 413, and the current I corresponding to the potential difference is 44 Flows through resistor 413.

[0066] The current flowing through the transistor 403 flows into the constant current source 405 through the drain-source of the depletion-type n-channel transistor 401. Therefore, the current I flowing through the source-drain of the transistor 403 46 becomes the current I flowing through the constant current source 405 47 Subtract the current I flowing through resistor 413 44 The value of .

[0067] The transistor 404 and the transistor 403 form a current mirror circuit, so a current equal to that between the source and drain of the transistor 403 flows between the source and drain of the transistor 404. That is, the current I flowing between the source and drain of the transistor 404 is 41 With current I 46 In addition, the current I 41 With current I 46 is equal to, so with the current I 47 Subtract the current I 44 The values ​​after are equal.

[0068] The current flowing between the drain and source of the depletion type n-channel transistor 402 flows through the resistor 413 and the constant current source 407. Therefore, the current I flowing between the drain and source of the depletion type n-channel transistor 402 is 43 The current I flowing through the resistor 413 becomes 44 and the current I flowing through the constant current source 407 48 The current after addition.

[0069] Here, the current I flowing between the source and the drain of the transistor 409 42 The current I flowing between the drain and source of the depletion-type n-channel transistor 402 43 Subtract the current I flowing between the source and drain of transistor 404 41 The value after the current I 43 The current I 48 and current I 44 The added current, current I 41 is the current I 47 Subtract the current I 44 The current after that, so the current I 42 Becomes current I 44 2 times the value of .

[0070] The transistor 410 and the transistor 409 form a current mirror circuit, so a current equal to that between the source and drain of the transistor 409 flows between the source and drain of the transistor 410. That is, the current I flowing between the source and drain of the transistor 409 is 45 With current I 42 That is, the current I 45 Becomes current I44 2 times the value of .

[0071] Current I 45 The current I flows through the resistor 411, so the potential of the output terminal TO becomes the resistance value of the resistor 411 multiplied by the current I 45 The value of the current value.

[0072] Therefore, the potential difference between the second input terminal TN and the first input terminal TI is amplified to twice the resistance ratio of the resistor 411 to the resistor 413 and is output to the output terminal TO.

[0073] [First Modification of Amplifier Circuit 406]

[0074] Figure 3 1 is a diagram showing an example of the configuration of an amplifier circuit 406A which is a first modification example of the amplifier circuit in the first embodiment.

[0075] The amplifier circuit 406A includes a transistor 703 , a transistor 704 , a transistor 701 , a transistor 702 , a transistor 709 , a transistor 710 , a resistor 713 , a resistor 711 , a resistor 715 , a resistor 717 , a constant current source 705 , a constant current source 707 , a constant current source 714 , and a constant current source 716 .

[0076] The transistor 703, the transistor 704, the transistor 709, and the transistor 710 are all p-channel transistors. The transistor 701 and the transistor 702 are all n-channel transistors.

[0077] In transistor 701, the gate is connected to the first input terminal TI via resistor 715, and is connected to the power supply terminal TP via constant current source 714, the source is connected to the power supply terminal TG via constant current source 705, and the drain is connected to the drain of transistor 703. In transistor 702, the gate is connected to the second input terminal TN via resistor 717, and is connected to the power supply terminal TP via constant current source 716, the source is connected to the power supply terminal TG via constant current source 707, and the drain is connected to the drain of transistor 704. The source of transistor 701 and the source of transistor 702 are connected to each other via resistor 713.

[0078] In transistor 703, the source is connected to the power supply terminal TP, the gate is connected to the drain of itself and the gate of transistor 704, and the drain is connected to the drain of transistor 701. In transistor 704, the source is connected to the power supply terminal TP, the gate is connected to the gate of transistor 703 and the drain of transistor 703, and the drain is connected to the drain of transistor 702.

[0079] The transistor 709 has a gate and a drain connected to the drain of the transistor 704, and a source connected to the power supply terminal TP. The transistor 710 has a gate connected to the drain of the transistor 704, a source connected to the power supply terminal TP, a drain connected to the output terminal TO, and connected to the power supply terminal TG via the resistor 711.

[0080] In the above-mentioned amplifier circuit 406, the first input terminal TI and the second input terminal TN are connected to the gate of the transistor 401 and the gate of the transistor 402, respectively, and the transistor 401 and the transistor 402 are both depletion type n-channel transistors. The reason why the depletion type n-channel transistors are used in the amplifier circuit 406 is that the first input terminal TI and the second input terminal TN of the amplifier circuit 406 become negative potentials.

[0081] On the other hand, in the amplifier circuit 406A of this modification, the first input terminal TI is connected to the power supply via the resistor 715 and the constant current source 714. The connection point P71 of the constant current source 714 and the resistor 715 can be set to a positive potential by the current value of the constant current source 714 and the resistance value of the resistor 715. The gate of the transistor 701 is connected to the connection point P71 of the constant current source 714 and the resistor 715, and can therefore be set to a positive potential. Therefore, in the embodiment of the amplifier circuit 406A, the transistor 701 may not be a depletion-type transistor.

[0082] Similarly, the second input terminal TN is connected to the power supply via the resistor 717 and the constant current source 716. The connection point P72 of the constant current source 716 and the resistor 717 can become a positive potential by the current value of the constant current source 716 and the resistance value of the resistor 717. The gate of the transistor 702 is connected to the connection point P72 of the constant current source 716 and the resistor 717, so it can become a positive potential. Therefore, in the embodiment of the amplifier circuit 406A, the transistor 702 may not use a depletion type transistor.

[0083] [Second embodiment]

[0084] Figure 4 1 is a diagram showing an example of the structure of the optical sensor 51 in the second embodiment. In addition, for the same structure as the optical sensor in the first embodiment, the same reference numerals are given and their descriptions are omitted. In this embodiment, the difference from the first embodiment is that the light detection unit includes a plurality of photodiodes and has a boost circuit 105.

[0085] The optical sensor 51 includes a first light detection unit 11 and a second light detection unit 21 .

[0086] The first light detection unit 11 includes a photodiode 1011, a photodiode 1012, ..., and a photodiode 101 n(n is a natural number greater than or equal to 2.) The photodiodes included in the first light detection unit 11 are connected in cascade. That is, the first light detection unit 11 includes a plurality of photodiodes connected in cascade.

[0087] The second light detection unit 21 includes a photodiode 1021, a photodiode 1022, ..., and a photodiode 102 n (n is a natural number greater than or equal to 2.) The photodiodes included in the second light detection unit 21 are connected in cascade. That is, the second light detection unit 21 includes a plurality of photodiodes connected in cascade.

[0088] The optical sensor 50 described in the first embodiment includes the booster circuit 105 , and boosts the voltage at the connection point P4 , and uses the boosted voltage as the power supply of the amplifier circuit 406 .

[0089] On the other hand, in the second embodiment, a plurality of photodiodes are connected in cascade in the first light detection unit 11 and the second light detection unit 21. The power generated by the photovoltaic effect in the first light detection unit 11 and the second light detection unit 21 is used as a power supply for the amplifier circuit 406. In the first light detection unit 11 and the second light detection unit 21, a plurality of photodiodes are connected in cascade, so a sufficiently high voltage that can be used as a power supply can be obtained even when the amount of light is small.

[0090] Therefore, in the second embodiment, a plurality of photodiodes connected in cascade are provided, and the above-mentioned booster circuit is no longer necessary.

[0091] The configuration of the amplifier circuit 406 in the second embodiment is the same as that of the amplifier circuit 406 in the first embodiment (including amplifier circuits 406A, 406B, and 406C which are modifications of the amplifier circuit 406 . The amplifier circuits 406B and 406C will be described later).

[0092] [Third Embodiment]

[0093] Figure 5 1 is a diagram showing an example of the structure of the optical sensor 52 according to the third embodiment. In addition, about the structure similar to the optical sensor of each embodiment mentioned above, the same code|symbol is attached|subjected and the description is abbreviate|omitted.

[0094] The optical sensor 52 includes a first light detection unit 10 , a first resistor 103 , a second light detection unit 20 , a second resistor 104 , an amplifier circuit 106 , a booster circuit 105 , a transistor 107 , and a light detection current output terminal 110 .

[0095] The amplifier circuit 106 includes: a power supply terminal TP; a power supply terminal TG; a first input terminal TI; a second input terminal TN; and an output terminal TO.

[0096] In the present embodiment, the optical sensor 52 outputs the difference between the current value of the photocurrent I1 generated corresponding to the wavelength of the light detected by the first optical detection unit 10 and the current value of the photocurrent I2 generated corresponding to the wavelength of the light detected by the second optical detection unit 20 as the amount of current introduced from the optical detection current output terminal 110. Therefore, a current detection circuit (not shown) is provided at the optical detection current output terminal 110, so that the optical sensor 52 can detect the difference between the current value of the photocurrent I1 generated corresponding to the wavelength of the light detected by the first optical detection unit 10 and the current value of the photocurrent I2 generated corresponding to the wavelength of the light detected by the second optical detection unit 20.

[0097] The transistor 107 is an n-channel transistor. The gate of the transistor 107 is connected to the output terminal TO of the amplifier circuit 106. The source of the transistor 107 is connected to the first input terminal of the amplifier circuit 106. The drain of the transistor 107 is connected to the light detection current output terminal 110.

[0098] If light of a wavelength range (not including light of a specific wavelength range) is incident, the magnitude of the photocurrent generated by the photovoltaic effect in the second light detection unit 20 is the same as the magnitude of the photocurrent generated by the photovoltaic effect in the first light detection unit 10. In the third embodiment, in a wavelength range other than the specific wavelength range, the potential of the first input terminal TI of the amplifier circuit 106 and the potential of the second input terminal TN of the amplifier circuit 106 are the same potential. In this case, the potential output to the output terminal TO of the amplifier circuit 106 becomes the same potential as the first input terminal TI and the second input terminal TN.

[0099] Therefore, the amplifier circuit 106 controls the gate voltage of the transistor 107 so that current does not flow between the drain and the source of the transistor 107. That is, no current flows through the light detection current output terminal 110.

[0100] On the other hand, when light of a wavelength range (including light of a specific wavelength range) is incident, the photocurrent generated by the photovoltaic effect of the second light detection unit 20 is smaller than the photocurrent generated by the photovoltaic effect of the first light detection unit 10. Therefore, the potential of the second input terminal TN of the amplifier circuit 106 is greater than the potential of the first input terminal TI of the amplifier circuit 106.

[0101] The potential of the second input terminal TN of the amplifier circuit 106 is greater than the potential of the first input terminal TI, so the potential of the output terminal TO increases, and the gate potential of the transistor 107 increases. As a result, a current flows between the drain and the source of the transistor 107. If a current flows between the drain and the source of the transistor 107, the potential of the first input terminal TI of the amplifier circuit 106 rises until it becomes the same as the potential of the second input terminal TN of the amplifier circuit 106, and becomes a stable state.

[0102] Here, a current flowing from the connection point P1 to the connection point P2 is referred to as a current I3, and a current flowing from the connection point P1 to the connection point P3 is referred to as a current I4.

[0103] The first resistor 103 and the second resistor 104 have the same resistance value, so as long as the potentials of the connection points P2 and P3 are the same, there is no difference between the magnitude of the current I3 flowing through the first resistor 103 and the magnitude of the current I4 flowing through the second resistor 104. That is, the current difference between the photocurrent I1 and the photocurrent I2 flows from the transistor 107 to the connection point P2 because the current I3 and the current I4 are equal.

[0104] Therefore, a difference current between the photocurrent I1 and the photocurrent I2 flows between the drain and the source of the transistor 107 . That is, in this embodiment, the photosensor 52 can detect the difference between the light detected by the first light detection unit 10 and the light detected by the second light detection unit 20 from the light detection current output terminal 110 .

[0105] The configuration of the booster circuit 105 in the third embodiment is not different from the configuration of the booster circuit 105 described in the first embodiment.

[0106] In the third embodiment, as described in the second embodiment, the light detection unit may include a plurality of photodiodes and may not include the booster circuit 105 .

[0107] In addition, in this embodiment, there is no limitation on the circuit connected to the light detection current output terminal 110. For example, a repeatedly rechargeable battery may be connected to the light detection current output terminal 110.

[0108] In this case, a circuit may be configured to perform a predetermined operation when a predetermined voltage is stored in the battery. For example, a circuit may be configured to perform wireless communication when a predetermined voltage is stored in the battery.

[0109] [Implementation Method of Amplifier Circuit 106]

[0110] Figure 6 It is a diagram showing an example of the configuration of the amplifier circuit 106 in the third embodiment.

[0111] The amplifier circuit 106 includes a transistor 201 , a transistor 202 , a transistor 203 , a transistor 204 , a transistor 205 , a constant current source 206 , and a constant current source 207 .

[0112] The transistor 203 , the transistor 204 , and the transistor 205 are all p-channel transistors.

[0113] The transistor 201 as the first input stage transistor and the transistor 202 as the second input stage transistor are both depletion-type n-channel transistors.

[0114] The gate of the depletion type n-channel transistor 201 is connected to the first input terminal TI of the amplifier circuit 106. The gate of the depletion type n-channel transistor 202 is connected to the second input terminal TN of the amplifier circuit 106.

[0115] In the depletion type n-channel transistor 201, the gate is connected to the first input terminal TI, the source is connected to the source of the depletion type n-channel transistor 202, and is connected to the power supply terminal TG via the constant current source 206, and the drain is connected to the drain of the transistor 203, and is connected to the connection point between the gate of the transistor 203 and the gate of the transistor 204. In the depletion type n-channel transistor 202, the gate is connected to the second input terminal TN, the source is connected to the source of the depletion type n-channel transistor 201, and is connected to the power supply terminal TG via the constant current source 206, and the drain is connected to the drain of the transistor 204, and is connected to the gate of the transistor 205.

[0116] The transistor 203 has a source connected to the power supply terminal TP, a gate connected to its own drain and the gate of the transistor 204, and a drain connected to the drain of the depletion-type n-channel transistor 201. The transistor 204 has a source connected to the power supply terminal TP, a gate connected to the gate of the transistor 203 and the drain of the transistor 203, and a drain connected to the drain of the depletion-type n-channel transistor 202.

[0117] The transistor 205 has a gate connected to the drain of the transistor 204 , a source connected to the power supply terminal TP, and a drain connected to the power supply terminal TG via the constant current source 207 and to the output terminal TO.

[0118] The transistor 203 and the transistor 204 form a current mirror circuit. A current corresponding to the current flowing between the source and the drain of the transistor 203 flows between the source and the drain of the transistor 204 .

[0119] When the gate potential of the depletion type n-channel transistor 201 and the gate potential of the depletion type n-channel transistor 202 are the same, the same current flows between the drain and source of the depletion type n-channel transistor 201 and between the drain and source of the depletion type n-channel transistor 202. Between the source and drain of the transistor 205, a current corresponding to the potential difference between the gate and source of the transistor 205 flows.

[0120] When the gate potential of the depletion type n-channel transistor 202 rises, the current flowing between the drain and the source of the depletion type n-channel transistor 202 increases. The current flowing between the drain and the source of the depletion type n-channel transistor 202 flows into the power supply terminal TG via the constant current source 206. At this time, the current is limited by the constant current source 206. Therefore, when the gate potential of the depletion type n-channel transistor 202 rises, the potential of the drain of the depletion type n-channel transistor 202 decreases.

[0121] If the potential difference between the gate and the source of the transistor 205 increases, the current flowing between the source and the drain of the transistor 205 increases. The current flowing between the source and the drain of the transistor 205 flows into the power supply terminal TG via the constant current source 207. At this time, the current is limited by the constant current source 207. Therefore, the output potential of the output terminal TO rises.

[0122] Therefore, when the gate potential of the depletion-type n-channel transistor 202 rises, the output potential of the output terminal TO rises.

[0123] return Figure 5 If the output potential of the amplifier circuit 106 rises, a difference current between the photocurrent I1 and the photocurrent I2 will be generated at the light detection current output terminal 110 .

[0124] [First Modification of Amplifier Circuit 106]

[0125] Figure 7 1 is a diagram showing a configuration of an amplifier circuit 106A which is a first modification of the amplifier circuit in the third embodiment. The amplifier circuit 106A is one form of the amplifier circuit 106. The same reference numerals are used for the same configurations as those in the above-mentioned embodiments, and description thereof is omitted.

[0126] The amplifier circuit 106A includes a transistor 601 , a transistor 602 , a transistor 603 , a transistor 604 , a transistor 605 , a constant current source 606 , a constant current source 607 , a constant current source 609 , a resistor 610 , a constant current source 611 , and a resistor 612 .

[0127] Both the transistor 601 and the transistor 602 are n-channel transistors.

[0128] The transistor 603 , the transistor 604 , and the transistor 605 are all p-channel transistors.

[0129] In the transistor 601, the gate is connected to the first input terminal TI via the resistor 610, and is connected to the power supply terminal TP via the constant current source 609, the source is connected to the power supply terminal TG via the constant current source 606, and the drain is connected to the drain of the transistor 603. In the transistor 602, the gate is connected to the second input terminal TN via the resistor 612, and is connected to the power supply terminal TP via the constant current source 611, the source is connected to the power supply terminal TG via the constant current source 606, and the drain is connected to the drain of the transistor 604 and the gate of the transistor 605.

[0130] In transistor 603, the source is connected to the power supply terminal TP, the gate is connected to the drain of itself and the gate of transistor 604, and the drain is connected to the drain of transistor 601. In transistor 604, the source is connected to the power supply terminal TP, the gate is connected to the gate of transistor 603 and the drain of transistor 603, and the drain is connected to the drain of transistor 602.

[0131] The transistor 605 has a gate connected to the drain of the transistor 604 and the drain of the transistor 602 , a source connected to the power supply terminal TP, a drain connected to the output terminal TO, and connected to the power supply terminal TG via the constant current source 607 .

[0132] In the embodiment of the amplifier circuit 106, the first input terminal TI and the second input terminal TN are connected to the gate of the transistor 201 and the gate of the transistor 202, respectively, and the transistor 201 and the transistor 202 are both depletion-type n-channel transistors. In the embodiment of the amplifier circuit 106, the reason for using depletion-type n-channel transistors is that the first input terminal TI and the second input terminal TN of the amplifier circuit 106 become negative potentials.

[0133] On the other hand, in the amplifier circuit 106A in this embodiment, the first input terminal TI is connected to the power supply via the resistor 610 and the constant current source 609. The connection point of the constant current source 609 and the resistor 610 can be set to a positive potential by the current value of the constant current source 609 and the resistance value of the resistor 610. The gate of the transistor 601 is connected to the connection point of the constant current source 609 and the resistor 610, so it can be set to a positive potential. Therefore, in the embodiment of the amplifier circuit 106A, the transistor 601 does not need to be a depletion-type transistor.

[0134] Similarly, the second input terminal TN is connected to the power supply via the resistor 612 and the constant current source 611. The connection point of the constant current source 611 and the resistor 612 can be set to a positive potential by the current value of the constant current source 611 and the resistance value of the resistor 612. The gate of the transistor 602 is connected to the connection point of the constant current source 611 and the resistor 612, and can therefore be set to a positive potential. Therefore, in the embodiment of the amplifier circuit 106A, the transistor 602 may not be a depletion-type transistor.

[0135] [Second Modification Example of Amplifier Circuit 106]

[0136] Figure 8 1 is a diagram showing the configuration of an amplifier circuit 106B which is a second modification of the amplifier circuit in the third embodiment. Note that the same components as those in the above-described embodiments are denoted by the same reference numerals and their description is omitted.

[0137] The amplifier circuit 106B includes a transistor 801 , a transistor 802 , a transistor 803 , a transistor 804 , a resistor 805 , and a resistor 806 .

[0138] The transistor 803 and the transistor 804 are both p-channel transistors. The transistor 801 as the first input stage transistor and the transistor 802 as the second input stage transistor are both depletion-type n-channel transistors.

[0139] The resistance value of the resistor 805 is equal to the resistance value of the resistor 806 .

[0140] In the depletion type n-channel transistor 801, the gate is connected to the power supply terminal TG, the source is connected to the first input terminal TI via the resistor 805, and the drain is connected to the drain of the transistor 803 and to the connection point between the gate of the transistor 803 and the gate of the transistor 804. That is, the first input terminal TI of the amplifier circuit 106B is connected to the source of the depletion type n-channel transistor 801 via the resistor 805.

[0141] The depletion type n-channel transistor 802 has a gate connected to the power supply terminal TG, a source connected to the second input terminal TN via the resistor 806, a drain connected to the drain of the transistor 804, and connected to the output terminal TO. That is, the second input terminal TN of the amplifier circuit 106B is connected to the source of the depletion type n-channel transistor 802 via the resistor 806.

[0142] The transistor 803 has a source connected to the power supply terminal TP, a gate connected to its own drain and the gate of the transistor 804, and a drain connected to the drain of the depletion-type n-channel transistor 801. The transistor 804 has a source connected to the power supply terminal TP, a gate connected to the gate of the transistor 803 and the drain of the transistor 803, a drain connected to the drain of the depletion-type n-channel transistor 802, and is connected to the output terminal TO.

[0143] The transistor 803 and the transistor 804 form a current mirror circuit. A current corresponding to the current flowing between the source and the drain of the transistor 803 flows between the source and the drain of the transistor 804 .

[0144] Here, in the optical sensor 52 formed by the amplifier circuit 106B, the first input terminal TI of the amplifier circuit 106B is connected to the connection point P2. When the first light detection unit 10 detects light, the photocurrent I1 flows from the connection point P1 of the ground potential to the first light detection unit 10 via the first resistor 103. Therefore, the potential of the connection point P2 becomes a value lower than the ground potential. For example, when the ground potential is 0V (volt), the potential of the connection point P2 becomes a negative potential.

[0145] Since the gate of the depletion type n-channel transistor 801 is connected to the ground point, a potential difference is generated between the gate and the source of the depletion type n-channel transistor 801, and the same current as that between the source and the drain of the transistor 803 flows between the drain and the source of the depletion type n-channel transistor 801. That is, in this embodiment, the first input terminal TI outputs current.

[0146] The second input terminal TN is connected to the connection point P3. When the second light detection unit 20 detects light, the photocurrent I2 flows from the ground potential, that is, the connection point P1, into the second light detection unit 20 via the second resistor 104. Therefore, the potential of the connection point P3 becomes a value lower than the ground potential. For example, when the ground potential is set to 0 V (volt), the potential of the connection point P3 becomes a negative potential.

[0147] Since the gate of the depletion type n-channel transistor 802 is connected to the ground point, a potential difference is generated between the gate and the source of the depletion type n-channel transistor 802, and the same current as that between the drain and the source of the depletion type n-channel transistor 802 flows between the drain and the source of the depletion type n-channel transistor 802. That is, in this embodiment, the output terminal TO outputs the current.

[0148] The potential of the output terminal TO is controlled so that the source potential of the depletion type n-channel transistor 802 is equal to the source potential of the depletion type n-channel transistor 801. Since the resistor 805 is equal to the resistor 806, the first input terminal TI and the second input terminal TN have the same potential.

[0149] When the first light detection unit 10 and the second light detection unit 20 detect light in a specific wavelength range, the potential of the connection point P3 is proportional to the light intensity and is higher than the potential of the connection point P2. The output potential of the output terminal TO is controlled so that the potential of the first input terminal TI and the potential of the second input terminal TN are equal.

[0150] return Figure 5 When the potential of the output terminal TO of the amplifier circuit 106 rises, a current flows from the light detection current output terminal 110 through the drain-source of the transistor 107 . The current flowing through the drain-source of the transistor 107 flows into the first photodiode 101 .

[0151] Therefore, a difference current between the photocurrent I1 and the photocurrent I2 flows between the drain and the source of the transistor 107. That is, in this embodiment, the optical sensor 52 can detect the difference between the light detected by the first light detection unit 10 and the light detected by the second light detection unit 20 through the light detection current output terminal 110.

[0152] [Second Modification Example of Amplifier Circuit 406]

[0153] Fig. 9 1 is a diagram showing the configuration of an amplifier circuit 406B which is a second modification of the amplifier circuit in the first embodiment. Note that the same reference numerals are used for the same configurations as those in the above-described embodiments, and description thereof will be omitted.

[0154] The amplifier circuit 406B includes a transistor 111 , a transistor 112 , a transistor 113 , a transistor 114 , a transistor 117 , a resistor 115 , a resistor 116 , and a resistor 118 .

[0155] The transistor 113, the transistor 114, and the transistor 117 are all p-channel transistors. The transistor 111 and the transistor 112 are all depletion-type n-channel transistors.

[0156] The resistance value of the resistor 115 is equal to the resistance value of the resistor 116 .

[0157] The depletion type n-channel transistor 111 has a gate connected to the power supply terminal TG, a source connected to the first input terminal TI via the resistor 115 , and a drain connected to the drain of the transistor 113 and to a connection point between the gates of the transistor 113 and the gates of the transistor 114 .

[0158] The depletion-type n-channel transistor 112 has a gate connected to a connection point between the transistor 117 and the resistor 118 , a source connected to the second input terminal TN via the resistor 116 , and a drain connected to the drain of the transistor 114 and to the gate of the transistor 117 .

[0159] The transistor 113 has a source connected to the power supply terminal TP, a gate connected to its own drain and the gate of the transistor 114, and a drain connected to the drain of the depletion-type n-channel transistor 111. The transistor 114 has a source connected to the power supply terminal TP, a gate connected to the gate of the transistor 113 and the drain of the transistor 113, a drain connected to the drain of the depletion-type n-channel transistor 112, and a gate connected to the transistor 117.

[0160] The transistor 117 has a drain connected to the output terminal TO, a gate connected to a connection point between the drain of the transistor 114 and the depletion type n-channel transistor 112 , and a source connected to a connection point between the gate of the depletion type n-channel transistor 112 and the resistor 118 .

[0161] In the embodiment of the amplifier circuit 106B, the output potential of the output terminal TO is controlled so that the potential of the first input terminal TI is equal to the potential of the second input terminal TN. That is, the output potential of the output terminal TO is controlled by the difference between the light detected by the first light detection unit 10 and the light detected by the second light detection unit 20.

[0162] On the other hand, in the present embodiment, the current flowing into the first input terminal TI is controlled so that the current flowing into the second input terminal TN is equal to the current flowing into the output terminal TO. That is, the current flowing into the output terminal TO is controlled by the difference between the light detected by the first light detection unit 10 and the light detected by the second light detection unit 20.

[0163] In this embodiment, the gate of the depletion type n-channel transistor 112 is connected to the connection point between the source of the transistor 117 and the resistor 118. Therefore, the source voltage of the transistor 117 is controlled so that the current values ​​flowing into the resistor 115 and the current values ​​flowing into the resistor 116 are equal.

[0164] Specifically, the source voltage of the depletion type n-channel transistor 112 is higher than the source voltage of the depletion type n-channel transistor 111 by the amount of the potential difference between the first input terminal TI and the second input terminal TN. The gate of the depletion type n-channel transistor 111 is connected to the power supply terminal TG, so the gate voltage of the depletion type n-channel transistor 112 is higher than the potential of the power supply terminal TG by the amount of the potential difference between the first input terminal TI and the second input terminal TN.

[0165] A potential equal to the potential difference between the first input terminal TI and the second input terminal TN is applied to the resistor 118, and a current having a value equal to the potential difference between the first input terminal TI and the second input terminal TN divided by the resistance value of the resistor 118 flows from the output terminal TO. That is, a current proportional to the potential difference of the input terminals flows from the output terminal TO.

[0166] Therefore, the amplifier circuit 406B can detect the difference between the light detected by the first light detection unit 10 and the light detected by the second light detection unit 20 by the value of the current flowing into the output terminal TO.

[0167] [Third Modification Example of Amplifier Circuit 406]

[0168] Fig.10 1 is a diagram showing the configuration of an amplifier circuit 406C which is a third modification of the amplifier circuit in the first embodiment. Note that the same reference numerals are used for the same configurations as those in the above-described embodiments, and description thereof will be omitted.

[0169] The amplifier circuit 406C includes a transistor 121 , a transistor 122 , a transistor 123 , a transistor 124 , a transistor 127 , a transistor 128 , a transistor 130 , a resistor 125 , a resistor 126 , a resistor 129 , and a resistor 131 .

[0170] The transistor 123, the transistor 124, the transistor 127, the transistor 128, and the transistor 130 are all p-channel transistors. The transistor 121 and the transistor 122 are all depletion-type n-channel transistors.

[0171] The resistance value of the resistor 125 is equal to the resistance value of the resistor 126 .

[0172] The depletion type n-channel transistor 121 has a gate connected to the power supply terminal TG, a source connected to the first input terminal TI via the resistor 125 , and a drain connected to the drain of the transistor 123 and to a connection point between the gates of the transistor 123 and the gates of the transistor 124 .

[0173] The depletion-type n-channel transistor 122 has a gate connected to a connection point between the source of the transistor 128 and the resistor 129 , a source connected to the second input terminal TN via the resistor 126 , and a drain connected to a connection point between the drain of the transistor 124 and the gate of the transistor 128 .

[0174] The transistor 123 has a source connected to the power supply terminal TP, a gate connected to its own drain and the gate of the transistor 124, and a drain connected to the drain of the depletion-type n-channel transistor 121. The transistor 124 has a source connected to the power supply terminal TP, a gate connected to the gate of the transistor 123 and the drain of the transistor 123, a drain connected to the drain of the depletion-type n-channel transistor 122, and a gate connected to the transistor 128.

[0175] The transistor 127 has a source connected to the power supply terminal TP, a gate connected to a connection point between the gate of the transistor 130 and its own drain, and a drain connected to a connection point between the drain of the transistor 128 and its own gate.

[0176] In transistor 128, the drain is connected to the connection point between the drain of transistor 127 and the gate of transistor 127, the gate is connected to the connection point between the drain of transistor 124 and the drain of depletion type n-channel transistor 122, and the source is connected to the connection point between the gate of depletion type n-channel transistor 122 and resistor 129.

[0177] The transistor 130 has a source connected to the power supply terminal TP, a gate connected to a connection point between the gate of the transistor 127 and the drain of the transistor 127 , and a drain connected to a connection point between the output terminal TO and the resistor 131 .

[0178] In the embodiment of the amplifier circuit 406B, the current flowing into the first input terminal TI and the current flowing into the second input terminal TN are controlled so that the current flowing into the output terminal TO is equal. That is, the current flowing into the output terminal TO is controlled by the difference between the light detected by the first light detection unit 10 and the light detected by the second light detection unit 20.

[0179] On the other hand, in this embodiment, the current flowing into the output terminal TO of the amplifier circuit 406B is copied by the current mirror circuit composed of the transistor 127 and the transistor 130. The copied current outputs a voltage corresponding to the resistance value of the resistor 131. That is, a voltage based on the resistance ratio of the resistor 131 to the resistor 129 is output at the output terminal TO.

[0180] In this embodiment, the gate of the depletion type n-channel transistor 122 is connected to the connection point between the source of the transistor 128 and the resistor 129. Therefore, the source voltage of the transistor 128 is controlled so that the current value flowing into the resistor 125 and the current value flowing into the resistor 126 are equal.

[0181] Specifically, the source voltage of the depletion type n-channel transistor 122 is higher than the source voltage of the depletion type n-channel transistor 121 by the amount of the potential difference between the first input terminal TI and the second input terminal TN. The gate of the depletion type n-channel transistor 121 is connected to the power supply terminal TG, so the gate voltage of the depletion type n-channel transistor 122 is higher than the potential of the power supply terminal TG by the amount of the potential difference between the first input terminal TI and the second input terminal TN.

[0182] A potential equal to the potential difference between the first input terminal TI and the second input terminal TN is applied to the resistor 129 , so that a current having a value obtained by dividing the potential difference between the first input terminal TI and the second input terminal TN by the resistance value of the resistor 129 flows.

[0183] Here, the transistor 127 and the transistor 130 form a current mirror circuit. Since the current flowing into the resistor 129 is equal to the current flowing through the transistor 127, a current equal to the current flowing into the resistor 129 flows through the transistor 130. That is, a current having a value equal to the potential difference between the first input terminal TI and the second input terminal TN divided by the resistance value of the resistor 129 flows through the transistor 130.

[0184] That is, a voltage obtained by multiplying the potential difference between the first input terminal TI and the second input terminal TN by the resistance ratio of the resistor 131 to the resistor 129 is output from the output terminal TO.

[0185] Therefore, a voltage corresponding to the intensity in a specific wavelength range is output from the output terminal TO.

[0186] [Summary of Effects of Embodiments]

[0187] According to the embodiment described above, the optical sensor 50 includes a first light detection unit 10 and a second light detection unit 20. The first light detection unit 10 has a characteristic of photoelectric generation in a wider wavelength range, that is, a first wavelength sensitivity characteristic, and the second light detection unit 20 has a second wavelength sensitivity characteristic that reduces sensitivity only to light in a specific wavelength range relative to the first wavelength sensitivity characteristic of the first light detection unit 10.

[0188] The optical sensor 50 can detect light in a specific wavelength range by comparing the current generated by the photovoltaic effect in the first light detection unit 10 and the current generated by the photovoltaic effect in the second light detection unit 20 .

[0189] Furthermore, the optical sensor 50 uses the electric power generated by the first light detection unit 10 and the second light detection unit 20 as a power source for the amplifier circuit 106 .

[0190] Conventionally, the driving circuit requires an external power supply, but according to the above-described embodiment, it is no longer necessary to prepare an external power supply.

[0191] That is, the optical sensor 50 according to the present embodiment does not require an external power source.

[0192] According to the above embodiment, the optical sensor 50 includes the booster circuit 105. The booster circuit 105 boosts the power generated by the first light detection unit 10 and the second light detection unit 20. The booster circuit 105 supplies the boosted power to the power supply terminal of the amplifier circuit 106.

[0193] Here, the driving voltage of the amplifier circuit 106 may be higher than the voltage generated by the first light detection unit 10 and the second light detection unit 20. In this case, the booster circuit 105 boosts the voltage to a voltage higher than the driving voltage of the amplifier circuit 106.

[0194] Therefore, the optical sensor 50 includes the voltage booster circuit 105 , and thus can drive the amplifier circuit 106 even when the voltage generated by the first light detection unit 10 and the second light detection unit 20 is lower than the operating voltage of the amplifier circuit 106 .

[0195] Furthermore, according to the above-described embodiment, the first light detection unit 10 includes a plurality of photodiodes connected in cascade, and the second light detection unit 20 includes a plurality of photodiodes connected in cascade.

[0196] The conventional booster circuit requires a clock generation circuit or a charge pump circuit, etc. However, by using the structure of a plurality of photodiodes connected in cascade in the above embodiment, the first light detection unit 10 and the second light detection unit 20 can obtain a sufficient voltage for driving the amplifier circuit 106 .

[0197] Therefore, the optical sensor 50 does not require a circuit such as a clock generation circuit for a booster circuit or a charge pump circuit.

[0198] Therefore, the circuit configuration of the optical sensor 50 is simplified compared to a conventional circuit configuration including a clock generation circuit, a charge pump circuit, etc. As a result, circuit design work such as circuit configuration is facilitated.

[0199] Furthermore, according to the above-described embodiment, the optical sensor 50 includes the n-channel transistor 107 and the light detection current output terminal 110 .

[0200] The optical sensor 50 includes the n-channel transistor 107 and the light detection current output terminal 110 , so that the configuration of the amplifier circuit 106 can be simplified.

[0201] Therefore, the optical sensor 50 can reduce costs by simplifying the circuit structure. In addition, by simplifying the structure of the amplifier circuit 106, the circuit structure of the optical sensor 50 is simplified, and circuit design work such as circuit configuration is facilitated.

[0202] According to the above-described embodiment, a depletion-type n-channel transistor is used at the input terminal of the amplifier circuit 106. With this configuration, the amplifier circuit 106 can detect a negative potential without adding an element for making the gate of the transistor a positive potential.

[0203] Therefore, the circuit structure of the optical sensor 50 is simplified. Since the circuit structure of the optical sensor 50 is simplified, circuit design work such as circuit configuration is facilitated.

[0204] According to the above-described embodiment, the input terminal of the amplifier circuit 106 is connected to the source of the depletion-type n-channel transistor via a resistor. With this configuration, the amplifier circuit 106 can suppress power consumption.

[0205] Above, with reference to the accompanying drawings, the embodiments of the present invention are described in detail, but the specific structure is not limited to the embodiments, and also includes designs that do not deviate from the scope of the gist of the present invention. These embodiments or their modifications are included in the scope or gist of the invention, and are also included in the invention described in the claims and their equivalents.

[0206] Description of symbols

[0207] 10, 11…1st light detection unit; 20, 21…2nd light detection unit; 50, 51, 52…light sensor; 101…1st photodiode; 102…2nd photodiode; 103…1st resistor; 104…2nd resistor; 105…boost circuit; 108…input terminal; 109…output terminal; 106, 106A, 106B, 406, 406A, 406B, 406C…amplifier circuit; 107, 201, 202, 203, 204, 205, 401, 402, 403, 404, 409, 410, 601, 602, 603, 604, 605, 701, 702, 703, 704, 709, 710, 801, 802, 803, 804, 809, 810, 811, 812, 813, 814, 815 03, 804, 111, 112, 113, 114, 117, 123, 124, 121, 122, 127, 128, 130…transistor; 206, 207, 405, 407, 606, 607, 609, 611, 705, 707, 714, 716…constant current source; 411, 413, 610, 612, 805, 806, 713, 715, 717, 711, 115, 116, 118, 125, 126, 129, 131…resistor; 408…output pin; 110…light detection current output terminal; TP…power supply terminal; TG…power supply terminal; TI…first input terminal; TN…second input terminal; TO…output terminal.

Claims

1. A light sensor comprising: a first light detection unit including a photodiode and having a first wavelength sensitivity characteristic; a first resistor, one end of which is connected to the cathode of the photodiode of the first light detection unit, and the other end of which is connected to a ground point; a second light detection unit including a photodiode having an anode connected to the anode of the photodiode of the first light detection unit and having a second wavelength sensitivity characteristic different from the first wavelength sensitivity characteristic; a second resistor having one end connected to the cathode of the photodiode of the second light detection unit and the other end connected to the ground point; and An amplifier circuit includes a first input terminal connected to the cathode of the photodiode of the first light detection unit, a second input terminal connected to the cathode of the photodiode of the second light detection unit, and an output terminal that outputs a potential based on the difference between the potential of the first input terminal and the potential of the second input terminal, and uses the power generated by the electromotive force of the photodiode of the first light detection unit and the photodiode of the second light detection unit as an operating power supply.

2. The optical sensor according to claim 1, further comprising: a voltage step-up unit configured to supply a power supply terminal of the amplifier circuit with power obtained by stepping up the power generated by the electromotive force.

3. The optical sensor according to claim 1, wherein: The first light detection unit includes a plurality of photodiodes connected in cascade. The second light detection unit includes a plurality of photodiodes connected in cascade.

4. The optical sensor according to claim 1, further comprising: n-channel transistor; and Light detection current output terminal, The gate of the transistor is connected to the output terminal of the amplifier circuit. The source of the transistor is connected to the first input terminal of the amplifier circuit. A drain of the transistor is connected to the light detection current output terminal.

5. The optical sensor according to claim 1, further comprising: a first input stage transistor; and 2nd input stage transistor, The gate of the first input stage transistor is connected to the first input terminal of the amplifier circuit. The gate of the second input stage transistor is connected to the second input terminal of the amplifier circuit. The first input stage transistor and the second input stage transistor are both depletion type n-channel transistors.

6. The optical sensor according to claim 1, further comprising: a first input stage transistor; and 2nd input stage transistor, The source of the first input stage transistor is connected to the first input terminal of the amplifier circuit via a resistor. The source of the second input stage transistor is connected to the second input terminal of the amplifier circuit via a resistor. The first input stage transistor and the second input stage transistor are both depletion type n-channel transistors.

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