CN113970372A - Light sensing circuit - Google Patents

Light sensing circuit Download PDF

Info

Publication number
CN113970372A
CN113970372A CN202110826053.9A CN202110826053A CN113970372A CN 113970372 A CN113970372 A CN 113970372A CN 202110826053 A CN202110826053 A CN 202110826053A CN 113970372 A CN113970372 A CN 113970372A
Authority
CN
China
Prior art keywords
terminal
circuit
coupled
light sensing
output
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
CN202110826053.9A
Other languages
Chinese (zh)
Inventor
黄圣文
刘铭晃
林孟勇
王照勋
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Sensorteknik Technology Corp
Original Assignee
Sensorteknik Technology Corp
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Sensorteknik Technology Corp filed Critical Sensorteknik Technology Corp
Publication of CN113970372A publication Critical patent/CN113970372A/en
Pending legal-status Critical Current

Links

Images

Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J1/00—Photometry, e.g. photographic exposure meter
    • G01J1/42—Photometry, e.g. photographic exposure meter using electric radiation detectors
    • G01J1/44—Electric circuits
    • G01J1/46—Electric circuits using a capacitor
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J1/00—Photometry, e.g. photographic exposure meter
    • G01J1/42—Photometry, e.g. photographic exposure meter using electric radiation detectors
    • G01J1/44—Electric circuits
    • G01J2001/4446—Type of detector
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J1/00—Photometry, e.g. photographic exposure meter
    • G01J1/42—Photometry, e.g. photographic exposure meter using electric radiation detectors
    • G01J1/44—Electric circuits
    • G01J2001/4446—Type of detector
    • G01J2001/446—Photodiode

Landscapes

  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Spectroscopy & Molecular Physics (AREA)
  • Amplifiers (AREA)
  • Geophysics And Detection Of Objects (AREA)
  • Push-Button Switches (AREA)
  • Fire-Detection Mechanisms (AREA)
  • Light Receiving Elements (AREA)

Abstract

The invention relates to a light sensing circuit, which comprises a bootstrap circuit and a light sensing component, wherein an equivalent capacitance value generated by a parasitic capacitance of the light sensing component is reduced by a circuit gain of the bootstrap circuit so as to reduce the noise of the light sensing circuit and increase the bandwidth of the light sensing circuit.

Description

Light sensing circuit
Technical Field
The present invention relates to a sensing circuit, and more particularly to a photo sensing circuit.
Background
With the development of technology, many electronic devices are developed to meet the market trend and the demand of people, and in order to increase the functions of the electronic devices, a light sensor is disposed in the electronic devices, wherein the light sensor is a sensor capable of sensing light or other electromagnetic energy, and is applied to the intensity of the light source of the environment to perform the corresponding function. For example, the light sensor may be disposed in a smart phone to automatically turn on a flash lamp when the intensity of the ambient light source is insufficient. Since the optical sensor is made of semiconductor, the optical sensor has parasitic capacitance, which causes problems such as circuit noise or circuit bandwidth reduction.
Based on the above problems, the present invention provides a photo sensing circuit, which can reduce the circuit noise problem or increase the bandwidth of the circuit through a bootstrap circuit.
Disclosure of Invention
An objective of the present invention is to provide a photo sensing circuit, which utilizes a circuit gain of a bootstrap circuit to improve the problem of parasitic capacitance of a photo sensing device.
An object of the present invention is to provide an optical sensing circuit, which includes a bootstrap circuit and an optical sensing device, wherein a circuit gain of the bootstrap circuit reduces an equivalent capacitance value generated by a parasitic capacitance of the optical sensing device, so as to reduce the influence caused by the noise of the circuit, or solve the problem of the reduction of the circuit bandwidth.
Drawings
FIG. 1: which is a circuit diagram of a light-sensing circuit of a first embodiment of the present invention;
FIG. 2: which is a schematic diagram of an equivalent capacitor according to a first embodiment of the present invention;
FIG. 3: which is a circuit diagram of a light-sensing circuit of a second embodiment of the present invention;
FIG. 4: which is a circuit diagram of a light-sensing circuit of a third embodiment of the present invention;
FIG. 5: it is a schematic diagram of an equivalent capacitor according to a third embodiment of the present invention; and
FIG. 6: which is a circuit diagram of a light sensing circuit according to a fourth embodiment of the present invention.
[ brief description of the drawings ]
10 bootstrap circuit
30 light sensing assembly
40 amplifier circuit
100 light sensing circuit
CPD parasitic capacitance
D1 photoelectric conversion module
equivalent CPD capacitance value
I1 photocurrent
I18 current source
L incident light
M12 transistor
M14 first transistor
M16 second transistor
OP operational amplifier
RS impedance component
Rf resistance
VDDSupply voltage
VREFReference signal
VOUTOutput signal
Detailed Description
In order to provide a further understanding and appreciation for the structural features and advantages achieved by the present invention, the following detailed description of the presently preferred embodiments is provided:
although certain terms are used herein to refer to particular components, those skilled in the art will understand that various terms are used herein to distinguish one component from another, and not necessarily from one another. In the following description and in the claims, the terms "include" and "comprise" are used in an open-ended fashion, and thus should be interpreted to mean "include, but not limited to. Furthermore, the term "coupled" is intended to include any direct or indirect connection. Thus, if a first device couples to a second device, that connection may be through a direct connection, or through an indirect connection via other devices and other connections.
In view of the fact that the area of the conventional photo sensing circuit is increased, the parasitic capacitance of the photodiode is also increased, but the excessive parasitic capacitance generates larger circuit noise, the present invention provides a photo sensing circuit to solve the problem of the increase of circuit noise caused by the parasitic capacitance of the photo sensing device in the prior art.
First, please refer to fig. 1, which is a circuit diagram of a light sensing circuit according to a first embodiment of the present invention. As shown, the photo sensing circuit 100 of the present invention includes a bootstrap circuit 10 and a photo sensing device 30. The bootstrap circuit 10 is coupled to the photo sensing device 30, and the photo sensing device 30 generates a photocurrent I1 according to an incident light L, wherein the photo sensing device 30 includes a photoelectric conversion device D1 and a parasitic capacitor CPD. In an embodiment of the invention, the bootstrap circuit 10 is coupled to the photo sensing device 30, and the photo-electric conversion device D1 of the photo sensing device 30 is used to convert the incident light L into a photo current I1, and the magnitude of the photo current I1 generated by the photo sensing device 30 is proportional to the intensity of the incident light L received by the photo sensing device 30, that is, the stronger the intensity of the incident light L received by the photo sensing device 30, the larger the photo current I1 generated by the photo sensing device 30, in this embodiment, the photo-electric conversion device D1 may be, for example, a photodiode, a complementary metal oxide semiconductor field effect transistor (CMOS FET) or a Charge Coupled Device (CCD), but not limited thereto.
In the present embodiment, the optical sensing circuit 100 further includes an amplifier circuit 40 coupled to the optical sensing element 30 and the receiving photocurrent I1, and generating an output signal V via a capacitor Cf according to the photocurrent I1 of the optical sensing element 30OUTIn an embodiment of the present invention, the integration is performed by an amplifier circuit 40, wherein the amplifier circuit 40 includes an operational amplifier OP and a capacitor Cf, the operational amplifier OP has a first input terminal, a second input terminal and an output terminal, the first input terminal receives a reference signal VREFThe second input terminal is coupled to the photocurrent I1 of the photo-sensing device 30, and the amplifier circuit 40 generates the accumulated charges according to the photocurrent I1 and the capacitance Cf to generate the output signal VOUTIn this example, the amplifier circuit 40 can convert the photocurrent I1 from the photo sensing device 30 into the output signal V via accumulated chargesOUTTo provide applications for optical Sensing, such as Proximity Sensing (Proximity Sensing).
Referring to FIG. 1 and FIG. 2, the first embodiment of the present invention is shownSchematic diagram of equivalent capacitance of the embodiment. In the present embodiment, the bootstrap circuit 10 includes a transistor M12 having a first terminal, a second terminal and a third terminal, the first terminal is coupled to a power voltage VDDIn an embodiment of the present invention, the bootstrap circuit 10 is used as an input stage, and an equivalent capacitance value equivalent CPD generated by the parasitic capacitance CPD of the photo sensing device 30 is reduced by a characteristic of the transistor M12 of the bootstrap circuit 10, for example, in the embodiment, the bootstrap circuit 10 is coupled to one end of the photo sensing device 30 through the second end of the transistor M12, and is coupled to the other end of the photo sensing device 30 and the impedance device RS through the third end of the transistor M12, so as to provide a circuit gain 1/Gm, which can reduce the equivalent capacitance value equivalent CPD generated by the parasitic capacitance CPD of the photo sensing device 30 by the connection relationship among the transistor M12, the impedance device RS and the photo sensing device 30, the above connection relationship makes the equivalent capacitance value equivalent CPD of the parasitic capacitance CPD expressed as the following formula (one):
equivalent CPD ═ CPD x (1-A) ] and A ═ RS/[ (1/Gm) + RS ] formula (I)
For example, the equivalent capacitance value equivalent CPD shown in fig. 2 can be obtained by using the circuit gain 1/Gm of the bootstrap circuit 10 to effectively reduce the parasitic capacitance CPD of the photo sensing device 30, for example, from 100pF to 10pF through the above equation (one), so as to reduce the equivalent capacitance value equivalent CPD generated by the parasitic capacitance CPD and reduce the noise of the photo sensing circuit 100.
Please refer to fig. 3, which is a circuit diagram of a light sensing circuit according to a second embodiment of the present invention. Fig. 1 and fig. 3 are different in that the transistor M12 of fig. 1 is coupled to the impedance element RS, the transistor M12 of fig. 3 is coupled to a current mirror 16, particularly coupled to a first transistor M14, the current mirror 16 includes a current source I18, a first transistor M14 and a second transistor M16, the output impedance of the first transistor M14 of the current mirror 16 is equivalent to the impedance element RS shown in fig. 1, in an embodiment of the present invention, the transistors M14 and M16 may be Metal Oxide Semiconductor Field Effect Transistors (MOSFETs), N-type metal oxide semiconductor field effect transistors (NMOSFETs) or P-type metal oxide semiconductor field effect transistors (PMOSFETs), the output impedance of the first transistor M14 of the current mirror 16 is equivalent to the impedance element RS of the bootstrap circuit 10, and the noise reduction characteristics are as described above, and will not be described herein again. The connection relationship between the transistor M12, the current mirror 16 and the parasitic capacitor CPD of the photo sensing device 30 makes the equivalent capacitance value CPD of the parasitic capacitor CPD expressed as the following formula (two): the equivalent CPD is [ CPD x (1-a) ] and a is Rout _ M1/[ (1/Gm) + Rout _ M1] formula (two), where Rout _ M1 is the equivalent output resistance of the transistor M12, so the embodiment also reduces the equivalent capacitance value equivalent CPD of the parasitic capacitor CPD by the circuit gain 1/Gm provided by the transistor M12, thereby reducing the circuit noise of the photo sensing circuit 100.
The above embodiments are applied to an integrating amplifier circuit, and may be applied to a transimpedance amplifier circuit in addition to the integrating amplifier circuit, which is an amplifier circuit for converting a current into a voltage. Please refer to fig. 4, which is a circuit diagram of a light sensing circuit according to a third embodiment of the present invention. In the present embodiment, the amplifier circuit 40 includes an operational amplifier OP and a resistor Rf, the operational amplifier OP has a first input terminal receiving the reference signal V, a second input terminal and an output terminalREFThe second input terminal is coupled to the photo sensing device 30 for receiving the photocurrent I1, and the resistor Rf is coupled between the second input terminal and the output terminal of the operational amplifier OP, and transmits the photocurrent I1 to the resistor Rf to form a voltage-step, and generate the output signal VOUTAt the output.
Referring to fig. 4 and 5, schematic diagrams of an equivalent capacitor according to a third embodiment of the invention are shown. In the present embodiment, the bootstrap circuit 10 is also adopted, wherein the first terminal of the transistor M12 is also coupled to the power voltage VDDA second terminal coupled to one end of the photo sensing device 30 and a second input terminal of the operational amplifier OP, and a third terminal of the transistor M12 coupled to the other end of the photo sensing device 30 and the impedance device RS, wherein the bootstrap circuit 10 is used as an input stage in the embodiment and is driven by the self-driven power sourceFor example, in the embodiment, the bootstrap circuit 10 is coupled to one end of the photo sensing element 30 through the second terminal of the transistor M12, and coupled to the other end of the photo sensing element 30 and the impedance element RS through the third terminal of the transistor M12, so as to provide a circuit gain 1/Gm, which can reduce the equivalent capacitance value equivalent CPD generated by the parasitic capacitor CPD of the photo sensing element 30 by the connection relationship among the transistor M12, the impedance element RS and the photo sensing element 30, and the equivalent capacitance value equivalent CPD is as shown in the above equation (one). Referring to the above equation (i), the equivalent capacitance value equivalent CPD of the parasitic capacitor CPD shown in fig. 5 relatively increases the bandwidth of the transimpedance amplifier to reduce the parasitic capacitor CPD, that is, the circuit gain 1/Gm of the bootstrap circuit 10 is utilized to effectively reduce the parasitic capacitor CPD of the photo sensing device 30, for example, from 100pF to 10pF, so as to reduce the equivalent capacitance value equivalent CPD generated by the parasitic capacitor CPD, thereby increasing the bandwidth of the photo sensing circuit 100.
Please refer to fig. 6, which is a circuit diagram of a light sensing circuit according to a fourth embodiment of the present invention. Fig. 4 is different from fig. 6 in that a third terminal of the transistor M12 in fig. 4 is coupled to the impedance element RS, a third terminal of the transistor M12 in fig. 6 is coupled to the current mirror 16, particularly to the first terminal of the first transistor M14, the current mirror 16 includes a current source I18, a first transistor M14 and a second transistor M16, an output impedance of the first transistor M14 of the current mirror 16 is equivalent to the impedance element RS shown in fig. 4, and the characteristic of increasing the bandwidth is the same as the above-described characteristic of the embodiment in fig. 4, which is not repeated herein.
As mentioned above, the photo sensing circuit 100 of the present invention discloses that the photoelectric conversion device D1 can be disposed on the chip or outside the chip. However, the area of the off-chip photoelectric conversion device D1 is larger than that of the on-chip photoelectric conversion device D1, so that the off-chip photoelectric conversion device D1 has larger circuit noise, and the bootstrap circuit 10 of the present invention can reduce the circuit noise of the photo sensing circuit 100 or improve the bandwidth of the photo sensing circuit 100 by using the equivalent capacitance value CPD of the parasitic capacitor CPD of the off-chip photoelectric conversion device D1.
In summary, the photo sensing circuit of the present invention includes a bootstrap circuit and a photo sensing device, and a parasitic capacitance value of the photo sensing device is reduced by a circuit gain of the bootstrap circuit, so that the noise problem of the photo sensing circuit is reduced by reducing an equivalent capacitance value of the parasitic capacitance.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not intended to limit the scope of the present invention, which is defined by the appended claims.

Claims (9)

1. A light sensing circuit, comprising:
a bootstrap circuit having a circuit gain; and
a light sensing component coupled to the bootstrap circuit and generating a photocurrent according to an incident light, the light sensing component having a parasitic capacitance;
wherein the circuit gain changes an equivalent capacitance value generated by the parasitic capacitance.
2. The light sensing circuit of claim 1, further comprising:
an amplifier circuit coupled to the photo sensor for generating an output signal according to the photo current.
3. The light sensing circuit of claim 2, wherein the amplifier circuit comprises:
an operational amplifier having a first input terminal, a second input terminal and an output terminal, wherein the first input terminal receives a reference signal, the second input terminal receives the photocurrent, and the output terminal generates the output signal; and
and the capacitor is coupled between the second input end and the output end of the operational amplifier.
4. The light sensing circuit of claim 2, wherein the amplifier circuit comprises:
an operational amplifier having a first input terminal, a second input terminal and an output terminal, wherein the first input terminal receives a reference signal, the second input terminal receives the photocurrent, and the output terminal generates the output signal; and
and the resistor is coupled between the second input end and the output end of the operational amplifier.
5. The optical sensing circuit of claim 2, wherein the bootstrap circuit comprises a transistor having a first terminal, a second terminal and a third terminal, the first terminal is coupled to a power voltage, the second terminal is coupled to one terminal of the optical sensing device and the amplifier circuit, and the third terminal is coupled to another terminal of the optical sensing device, an impedance device and a ground terminal.
6. The light sensing circuit of claim 5, wherein the impedance element is equivalent to an output impedance of a plurality of transistors of a current mirror.
7. The optical sensing circuit of claim 1, wherein the bootstrap circuit comprises a transistor having a first terminal, a second terminal and a third terminal, the first terminal is coupled to the power voltage, the second terminal is coupled to a terminal of the optical sensing device, and the third terminal is coupled to another terminal of the optical sensing device, an impedance device and a ground terminal.
8. The light sensing circuit of claim 7, wherein the impedance element is equivalent to an output impedance of a plurality of transistors of a current mirror.
9. The photosensing circuit according to claim 1, wherein said photosensing element comprises a photoelectric conversion element, said photoelectric conversion element being disposed on a chip or outside said chip.
CN202110826053.9A 2020-07-23 2021-07-21 Light sensing circuit Pending CN113970372A (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US202063055887P 2020-07-23 2020-07-23
US63/055,887 2020-07-23

Publications (1)

Publication Number Publication Date
CN113970372A true CN113970372A (en) 2022-01-25

Family

ID=79586298

Family Applications (1)

Application Number Title Priority Date Filing Date
CN202110826053.9A Pending CN113970372A (en) 2020-07-23 2021-07-21 Light sensing circuit

Country Status (2)

Country Link
CN (1) CN113970372A (en)
TW (1) TWI804929B (en)

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US7418213B2 (en) * 2004-08-12 2008-08-26 Finisar Corporation Transimpedance amplifier with integrated filtering and reduced parasitic capacitance
US9300259B2 (en) * 2012-04-04 2016-03-29 Ams Ag Sensor amplifier arrangement and method for amplification of a sensor signal
KR101842137B1 (en) * 2013-12-13 2018-03-26 애플 인크. Integrated touch and display architectures for self-capacitive touch sensors
CN107147448B (en) * 2017-04-21 2019-06-14 天津大学 A kind of broadband optical receiver front-end circuit of high sensitivity

Also Published As

Publication number Publication date
TW202205807A (en) 2022-02-01
TWI804929B (en) 2023-06-11

Similar Documents

Publication Publication Date Title
US10805565B2 (en) CMOS image sensor, pixel circuit and driving method thereof
US20080007640A1 (en) Photoelectric conversion circuit and solid-state image-sensing device using it
US8975103B2 (en) CMOS image sensor with wide dynamic range
US7755020B2 (en) Light receiving circuit and light coupling device
US9562808B2 (en) Light receiving circuit and light coupling device
US6730897B2 (en) Linearity and dynamic range for complementary metal oxide semiconductor active pixel image sensors
US6849845B2 (en) Low power integrating circuit for use with a photodetector and optical sensor including such an integrating circuit
CN113970372A (en) Light sensing circuit
WO2018228772A1 (en) A low-noise transimpedance amplifier incorporating a regulator
JP2002171142A (en) Photoreceiver
CN101212580A (en) CMOS image sensor
CN114220373A (en) Light detection module, light detection method and display device
JP3534209B2 (en) Light receiving circuit
CN107820031B (en) CMOS image pixel circuit
KR100977834B1 (en) ???? Image Sensor with Wide Dynamic Range
US7468500B2 (en) High performance charge detection amplifier for CCD image sensors
JP4092243B2 (en) Optical amplifier circuit
KR20000041445A (en) Unit pixel of cmos image sensor having pn diode connected to floating sensing node
US20050275052A1 (en) Imaging sensor
CN212677264U (en) Power supply noise suppression circuit and image sensor
KR20040093908A (en) Unit pixel for cmos image sensor
JP2005217468A (en) Photocurrent/voltage conversion circuit
KR20050024208A (en) Solid state image pickup device
US20110204213A1 (en) Light amplification circuit and photocoupler
KR20040063639A (en) Photo diode circuit

Legal Events

Date Code Title Description
PB01 Publication
PB01 Publication
SE01 Entry into force of request for substantive examination
SE01 Entry into force of request for substantive examination