CN113395468A - Method for sampling and amplifying image sensor signal - Google Patents
Method for sampling and amplifying image sensor signal Download PDFInfo
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- CN113395468A CN113395468A CN202010165452.0A CN202010165452A CN113395468A CN 113395468 A CN113395468 A CN 113395468A CN 202010165452 A CN202010165452 A CN 202010165452A CN 113395468 A CN113395468 A CN 113395468A
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- 238000005070 sampling Methods 0.000 title claims abstract description 63
- 238000000034 method Methods 0.000 title claims abstract description 22
- 239000003990 capacitor Substances 0.000 claims abstract description 46
- 239000004065 semiconductor Substances 0.000 claims description 3
- 230000006641 stabilisation Effects 0.000 abstract description 12
- 238000011105 stabilization Methods 0.000 abstract description 12
- 238000004904 shortening Methods 0.000 abstract description 3
- 230000003321 amplification Effects 0.000 description 7
- 238000003199 nucleic acid amplification method Methods 0.000 description 7
- 238000013139 quantization Methods 0.000 description 3
- 238000010586 diagram Methods 0.000 description 2
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 229910052710 silicon Inorganic materials 0.000 description 1
- 239000010703 silicon Substances 0.000 description 1
- 230000001629 suppression Effects 0.000 description 1
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N25/00—Circuitry of solid-state image sensors [SSIS]; Control thereof
- H04N25/70—SSIS architectures; Circuits associated therewith
- H04N25/76—Addressed sensors, e.g. MOS or CMOS sensors
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N25/00—Circuitry of solid-state image sensors [SSIS]; Control thereof
- H04N25/60—Noise processing, e.g. detecting, correcting, reducing or removing noise
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N25/00—Circuitry of solid-state image sensors [SSIS]; Control thereof
- H04N25/70—SSIS architectures; Circuits associated therewith
- H04N25/71—Charge-coupled device [CCD] sensors; Charge-transfer registers specially adapted for CCD sensors
- H04N25/75—Circuitry for providing, modifying or processing image signals from the pixel array
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N25/00—Circuitry of solid-state image sensors [SSIS]; Control thereof
- H04N25/70—SSIS architectures; Circuits associated therewith
- H04N25/76—Addressed sensors, e.g. MOS or CMOS sensors
- H04N25/77—Pixel circuitry, e.g. memories, A/D converters, pixel amplifiers, shared circuits or shared components
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Abstract
The invention provides a sampling and amplifying method of image sensor signal, before sampling and amplifying signal, at least one voltage of output node or internal node or output sampling capacitor of amplifier circuit is preset, to realize sampling and amplifying of signal, and further isolate high resistance node and output sampling capacitor in amplifier circuit through buffer, thereby shortening stabilization time, improving stabilization performance, through adopting groove capacitor as input sampling capacitor, output sampling capacitor and feedback capacitor of amplifier circuit, realizing higher gain and lower noise in limited chip area, improving integral performance of image sensor.
Description
Technical Field
The invention relates to a method for sampling and amplifying signals of an image sensor.
Background
Currently, in a readout circuit of a CMOS Image Sensor (CIS), a column readout structure is widely used.
Conventional image signal column processing circuits are mainly of two types:
a does not have preamplification circuit, sample the image signal directly and quantize, it is not good to process the effect while being small like this, the equivalent read-out noise of the signal is greater, the quantization noise and resolution of the analog-to-digital converter (ADC) require higher;
the other pre-amplification circuit is limited by the restriction of capacitance values, higher gain and lower noise cannot be realized, the processing of tiny image signals is still not ideal, the large capacitance value not only can increase the chip area, but also can lead the stability time of the pre-amplification circuit to be longer and the stability performance to be poorer, and further the overall performance of the image sensor is influenced.
Disclosure of Invention
The invention aims to provide a method for sampling and amplifying signals of an image sensor, which shortens the stabilization time, improves the stabilization performance, realizes higher gain and lower noise in a limited chip area and improves the overall performance of the image sensor.
Based on the above consideration, the present invention provides a method for sampling and amplifying a signal of an image sensor, wherein at least one voltage of an output node or an internal node or an output sampling capacitor of an amplifier circuit is preset before sampling and amplifying the signal, so as to sample and amplify the signal.
Preferably, the internal node comprises a high-resistance node, and the high-resistance node is isolated from the output sampling capacitor by a buffer.
Preferably, the buffer is a source follower.
Preferably, the preset voltage value is smaller than the amplified reference signal value and the amplified image signal value.
Preferably, the preset voltage value is zero.
Preferably, at least one voltage of an output node or an internal node of the amplifier circuit or an output sampling capacitor is preset by a MOS switch.
Preferably, trench capacitors are used as the input sampling capacitor, the output sampling capacitor and the feedback capacitor of the amplifier circuit, and the trench capacitors are embedded silicon-based trench structures formed by extending a MOS gate and an insulating layer below the surface of a semiconductor.
The method for sampling and amplifying the signal of the image sensor comprises the steps of presetting at least one voltage of an output node or an internal node or an output sampling capacitor of an amplifier circuit before sampling and amplifying the signal to realize the sampling and amplification of the signal, and further isolating a high-resistance node and the output sampling capacitor in the amplifier circuit through a buffer, thereby shortening the stabilization time and improving the stabilization performance.
Drawings
Other features, objects and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments thereof, which proceeds with reference to the accompanying drawings.
Fig. 1 is a circuit diagram illustrating a method for sampling and amplifying an image sensor signal according to the present invention.
Detailed Description
In order to solve the problems in the prior art, the invention provides a method for sampling and amplifying signals of an image sensor, wherein before the signals are sampled and amplified, at least one voltage of an output node or an internal node or an output sampling capacitor of an amplifier circuit is preset to realize the sampling and amplification of the signals, and a high-resistance node and an output sampling capacitor in the amplifier circuit are further isolated by a buffer, so that the stabilization time is shortened, the stabilization performance is improved, and a groove capacitor is used as an input sampling capacitor, an output sampling capacitor and a feedback capacitor of the amplifier circuit, so that higher gain and lower noise are realized in a limited chip area, and the overall performance of the image sensor is improved.
In the following detailed description of the preferred embodiments, reference is made to the accompanying drawings which form a part hereof. The accompanying drawings illustrate, by way of example, specific embodiments in which the invention may be practiced. The illustrated embodiments are not intended to be exhaustive of all embodiments according to the invention. It is to be understood that other embodiments may be utilized and structural or logical changes may be made without departing from the scope of the present invention. The following detailed description, therefore, is not to be taken in a limiting sense, and the scope of the present invention is defined by the appended claims.
The present invention will be described in detail with reference to specific examples.
Fig. 1 illustrates a preferred embodiment of the method for sampling and amplifying an image sensor signal according to the present invention, which is illustrated by a dynamic column programmable gain amplifier (COL PGA) including a two-stage amplifier, but not limited thereto, and it will be understood by those skilled in the art that other single-stage or multi-stage amplifiers may be used to implement the method for sampling and amplifying an image sensor signal according to the present invention.
The MOS transistor M0/M1/M2/M3 forms the first stage of the amplifier and is a high-gain amplifier with a sleeve structure; M7/M8 constitutes the second stage of the amplifier, where M7 provides the bias current and M8 is the source follower. Cs1 is an input sampling capacitor, Cs2 is an output sampling capacitor, and Cfd is a feedback capacitor, where the feedback capacitor Cfd is a programmable capacitor controlled by a switch, for example, and the ratio of the input sampling capacitor Cs1 to the feedback capacitor Cfd is the amplification gain of the amplifier, which may be 1/2/4/8/16/32/64 times in an embodiment. Φ az is the self-clearing switch of the amplifier. Pxda are signals from the pixel cells of the image sensor, respectively the reference signal ref or the image signal sig at different times. The COL PGA is a preamplifier of the ADC, the preamplifier can reduce equivalent read noise (read noise) under high gain, improve quantization precision, reduce the requirement on the ADC, and can realize alternate sampling and quantization of a reference signal and an image signal and reduce line operation time by reasonably configuring the PGA and outputting the time sequence of sampling.
In the circuit schematic diagram of the image sensor signal sampling and amplifying method of the present invention, the image sensor further includes MOS switches M5/M6, which are initially configured switch circuits, and are used to preset at least one voltage of the output node Vo, or an internal node (e.g., high resistance node Vh), or the output sampling capacitor Cs2 of the amplifier circuit before sampling and amplifying the signal. The method of the invention can effectively shorten the stabilization time of the amplifier circuit and improve the stabilization performance when realizing the sampling and amplification of the signal by presetting at least one voltage of the output node Vo or the internal node (such as a high-resistance node Vh) or the output sampling capacitor Cs2 of the amplifier circuit before sampling and amplifying the signal. In addition, the source follower M8 isolates the high-resistance node Vh and the output sampling capacitor Cs2 inside the amplifier circuit as a buffer, thereby further shortening the settling time.
Preferably, the input sampling capacitor Cs1, the output sampling capacitor Cs2, and the feedback capacitor Cfd can be implemented by using a trench capacitor, where the trench capacitor is a silicon-embedded trench structure formed by extending a MOS gate and an insulating layer below a semiconductor surface, so as to implement a high capacitance value (ensuring noise suppression) and a high capacitance precision (ensuring uniformity of gain of a column amplifier) in a limited column space, thereby implementing a higher gain and lower noise in a limited chip area, and improving the overall performance of the image sensor.
In summary, according to the method for sampling and amplifying the signal of the image sensor of the present invention, before sampling and amplifying the signal, at least one voltage of an output node or an internal node or an output sampling capacitor of the amplifier circuit is preset to realize sampling and amplification of the signal, and a high resistance node and an output sampling capacitor inside the amplifier circuit are further isolated by a buffer, so as to shorten the stabilization time and improve the stabilization performance.
It will be evident to those skilled in the art that the invention is not limited to the details of the foregoing illustrative embodiments, and that the present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive. Furthermore, it will be obvious that the word "comprising" does not exclude other elements or steps, and the word "a" or "an" does not exclude a plurality. Several elements recited in the apparatus claims may also be implemented by one element. The terms first, second, etc. are used to denote names, but not any particular order.
Claims (7)
1. A method for sampling and amplifying signals of an image sensor is characterized in that at least one voltage of an output node or an internal node or an output sampling capacitor of an amplifier circuit is preset before the signals are sampled and amplified, and the signals are sampled and amplified.
2. The method of sampling and amplifying an image sensor signal according to claim 1, wherein the internal node comprises a high impedance node, the high impedance node being isolated from an output sampling capacitance by a buffer.
3. The method of sampling and amplifying an image sensor signal according to claim 2, wherein the buffer is a source follower.
4. The method of sampling and amplifying an image sensor signal according to claim 1, wherein the predetermined voltage value is smaller than the amplified reference signal value and the image signal value.
5. The method of sampling and amplifying an image sensor signal according to claim 4, wherein the predetermined voltage value is zero.
6. The method of sampling and amplifying an image sensor signal according to claim 1, wherein at least one of a voltage of an output node or an internal node or an output sampling capacitor of the amplifier circuit is preset by a MOS switch.
7. The method of sampling and amplifying an image sensor signal according to claim 1, wherein trench capacitors are used as an input sampling capacitor, an output sampling capacitor and a feedback capacitor of the amplifier circuit, the trench capacitors being silicon-embedded trench structures formed with MOS gates and insulating layers extending below a semiconductor surface.
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| CN202010165452.0A CN113395468B (en) | 2020-03-11 | 2020-03-11 | Sampling and amplifying method for image sensor signal |
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| CN113395468B (en) | 2024-08-20 |
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