Weak optical signal adaptive gain acquisition and amplification system based on analog switch

Abstract

The utility model relates to the technical field of analog electronics, in particular to a weak optical signal adaptive gain acquisition and amplification system based on an analog switch, which comprises a signal conversion unit, an operational amplification unit, a control unit and an analog switch unit, the signal conversion unit is used for converting the optical signal into a current signal; the operational amplification unit is connected with the signal conversion unit, receives and amplifies the current signal, and outputs an amplified voltage signal; the control unit is connected with the output end of the operational amplification unit, receives the amplified voltage signal and sends a control signal to the analog switch unit according to the amplified voltage signal; and the analog switch unit accesses resistors with different resistance values to a feedback loop of the operational amplification unit according to the control signal. By arranging a cooperative work system of the signal conversion unit, the operational amplification unit, the control unit and the analog switch unit, efficient conversion and adaptive gain amplification from an optical signal to a current signal are realized.

Description

Technical Field

[0001] The utility model relates to the technical field of analog electronics, in particular to a weak optical signal adaptive gain acquisition and amplification system based on analog switches. Background Art

[0002] Traditional weak optical signal acquisition systems typically use fixed-gain amplifier circuits to convert the weak current signals generated by photoelectric conversion elements such as photodiodes or photomultiplier tubes into measurable voltage signals. However, in practical applications, optical signal intensity often fluctuates significantly. For example, in fields such as environmental monitoring, medical diagnosis, and spectral analysis, light intensity can vary by several orders of magnitude. When the incident light intensity is high, fixed-gain systems are prone to saturation and distortion of the output signal. Conversely, when the incident light intensity is low, the system gain may be insufficient, causing the valid signal to be drowned out by noise, reducing the signal-to-noise ratio and affecting measurement accuracy.

[0003] Existing variable gain systems often suffer from transient interference during gain switching and discontinuous gain adjustment. These drawbacks can lead to critical information loss or measurement deviations, particularly in real-time monitoring and rapidly changing optical signal acquisition scenarios. Therefore, developing a weak optical signal acquisition system that can adaptively adjust gain and cover a wide dynamic range is of great practical value. Utility Model Content

[0004] The purpose of the utility model is to solve the problem of signal saturation distortion or insufficient signal-to-noise ratio that occurs in a traditional fixed-gain optical signal acquisition system when the light intensity fluctuates greatly.

[0005] The utility model provides a weak optical signal adaptive gain acquisition and amplification system based on analog switches, comprising a signal conversion unit, an operational amplifier unit, a control unit and an analog switch unit;

[0006] The signal conversion unit is used to convert the optical signal into a current signal; the operational amplifier unit is connected to the signal conversion unit, receives and amplifies the current signal, and outputs an amplified voltage signal;

[0007] The control unit is connected to the output end of the operational amplifier unit, receives the amplified voltage signal, and sends a control signal to the analog switch unit according to the amplified voltage signal; the analog switch unit connects resistors of different resistance values ​​to the feedback loop of the operational amplifier unit according to the control signal.

[0008] Furthermore, the signal conversion unit is a photodiode.

[0009] Furthermore, the operational amplifier unit includes a first amplifier and a second amplifier;

[0010] The non-inverting input terminal of the first amplifier is connected to the positive electrode of the photodiode, the inverting input terminal of the first amplifier is connected to the negative electrode of the photodiode and one end of the capacitor respectively, and the other end of the capacitor and the output terminal of the first amplifier are connected to one end of the first resistor;

[0011] The non-inverting input terminal of the second amplifier is connected to the first resistor, the inverting input terminal is connected in series with the second resistor and then grounded, and a third resistor is connected in parallel between the output terminal and the inverting input terminal of the second amplifier.

[0012] Furthermore, the analog switch unit includes a front-stage selection analog switch and a plurality of rear-stage analog switches;

[0013] The front-stage selection analog switch is used to select different rear-stage analog switch paths, and each rear-stage analog switch has multiple gear settings.

[0014] Furthermore, the front-stage selection analog switch includes a first analog switch chip;

[0015] The first pin of the first analog switch chip receives a first control signal, the second pin is connected to an external voltage source, the third pin is grounded, the fifth pin is connected to the operational amplifier unit, and the fourth and sixth pins are connected to the subsequent analog switch.

[0016] Further, the post-stage analog switch includes a first post-stage analog switch;

[0017] The first post-stage analog switch includes a second analog switch chip, wherein a first pin of the second analog switch chip receives a second control signal, a second pin is connected to an external voltage source, a third pin is grounded, a fourth pin is connected in series with a fourth resistor, and then connected to one end of a fifth resistor and a sixth resistor respectively, and the other end of the fifth resistor is grounded; a sixth pin is connected to one end of a seventh resistor, and the other end of the seventh resistor is connected to the other end of the sixth resistor, and the inverting input end of the first amplifier in the operational amplifier unit is connected between the sixth and seventh resistors.

[0018] Furthermore, the post-stage analog switch further includes a second post-stage analog switch;

[0019] The second post-stage analog switch includes a third analog switch chip, a first pin of the third analog switch chip receives a third control signal, a second pin is connected to an external voltage source, a third pin is grounded, a fourth pin is connected to one end of an eighth resistor, a sixth pin is connected to one end of a ninth resistor, and the other end of the ninth resistor is connected to the other end of the eighth resistor. The eighth resistor and the ninth resistor are also connected to the inverting input end of the first amplifier in the operational amplifier unit.

[0020] Furthermore, the control unit is a microcontroller unit, and the microcontroller unit generates the control signal according to the amplitude of the amplified voltage signal and a preset threshold.

[0021] Compared with the existing technology, the present invention has at least the following beneficial effects: by setting up a collaborative working system of a signal conversion unit, an operational amplifier unit, a control unit and an analog switch unit, efficient conversion of optical signals into current signals and adaptive gain amplification are achieved, wherein the control unit sends a control signal in real time according to the amplitude of the amplified voltage signal, and the analog switch unit dynamically adjusts the resistance value in the feedback loop accordingly, so that the system can automatically adjust the optimal gain level for optical signals of different intensities, solving the signal saturation distortion or insufficient signal-to-noise ratio problems that occur in traditional fixed-gain systems when the light intensity fluctuates. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are merely embodiments of the present invention. For ordinary technicians in this field, other drawings such as the provided drawings can be obtained without creative work.

[0023] Figure 1 This is a module diagram of a gain acquisition and amplification system in one embodiment of the present utility model;

[0024] Figure 2 This is a circuit diagram of an operational amplifier unit in one embodiment of the present invention;

[0025] Figure 3 This is a circuit diagram of a front-stage selection analog switch in one embodiment of the present utility model;

[0026] Figure 4 This is a circuit diagram of a first post-stage analog switch in a post-stage analog switch in an embodiment of the present utility model;

[0027] Figure 5 1 is a circuit diagram of a second post-stage analog switch in a post-stage analog switch in an embodiment of the present invention.

[0028] Among them, PIN5-photodiode; YF6C-first amplifier; YF6D-second amplifier; C76-capacitor; R146-first resistor; R148-second resistor; R153-third resistor; R14-fourth resistor; R40-fifth resistor; R41-sixth resistor; R19-seventh resistor; R20-eighth resistor; R23-ninth resistor. DETAILED DESCRIPTION

[0029] The present invention will be described in more detail below with reference to schematic diagrams, which illustrate preferred embodiments of the present invention. It should be understood that those skilled in the art may modify the present invention as described herein while still achieving the beneficial effects of the present invention. Therefore, the following description should be understood as generally known to those skilled in the art and not as limiting the present invention.

[0030] It should be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprises," "includes," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that includes a list of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus.

[0031] The following paragraphs describe the present invention in more detail by way of example with reference to the accompanying drawings. The advantages and features of the present invention will become more apparent as described below. It should be noted that the drawings are greatly simplified and not to exact scale, and are intended solely to facilitate and clearly illustrate the embodiments of the present invention.

[0032] This embodiment provides a weak optical signal adaptive gain acquisition and amplification system based on analog switches. Figure 1-Figure 5 , including a signal conversion unit, an operational amplifier unit, a control unit and an analog switch unit.

[0033] The signal conversion unit is used to convert the optical signal into a current signal; the operational amplifier unit is connected to the signal conversion unit, receives and amplifies the current signal, and outputs an amplified voltage signal Pin_ADC.

[0034] The control unit is connected to the output end of the operational amplifier unit, receives the amplified voltage signal Pin_ADC, and sends a control signal to the analog switch unit according to the amplified voltage signal Pin_ADC; the analog switch unit connects resistors of different resistance values ​​to the feedback loop of the operational amplifier unit according to the control signal.

[0035] Specifically, the signal conversion unit may use a photoelectric sensor device such as a photodiode, a phototransistor or a photomultiplier tube to realize photocurrent conversion. The operational amplifier unit may use a single-stage or multi-stage operational amplifier structure, wherein the multi-stage amplification may include a pre-stage transimpedance amplification and a post-stage voltage amplification. The control unit may use a microcontroller, an FPGA or a dedicated comparator circuit to realize signal amplitude detection and logic control functions. The analog switch unit may use a mechanical relay, a solid-state relay or an integrated circuit analog switch chip, wherein a multiplexed analog switch chip can realize multi-speed resistance switching. The feedback resistor network may use discrete resistors, a programmable resistor array or a digital potentiometer to realize resistance adjustment function.

[0036] Adaptive gain regulation is achieved by monitoring the output signal amplitude in real time and dynamically adjusting the operational amplifier feedback resistor. When changes in input light intensity cause the output signal to approach saturation or the signal-to-noise ratio to deteriorate, the control unit automatically switches the feedback resistor value to ensure the system always operates at optimal gain.

[0037] Furthermore, the operational amplifier unit includes a first amplifier YF6C and a second amplifier YF6D.

[0038] The non-inverting input terminal of the first amplifier YF6C is connected to the positive electrode of the photodiode PIN5, the inverting input terminal of the first amplifier YF6C is connected to the negative electrode of the photodiode PIN5 and one end of the capacitor C76 respectively, and the other end of the capacitor C76 and the output terminal of the first amplifier YF6C are connected to one end of the first resistor R146;

[0039] The non-inverting input terminal of the second amplifier YF6D is connected to the first resistor R146, the inverting input terminal is connected in series with the second resistor R148 and then grounded, and a third resistor R153 is connected in parallel between the output terminal and the inverting input terminal of the second amplifier YF6D.

[0040] Specifically, the first amplifier YF6C adopts a transimpedance amplifier structure, and the capacitor C76 and the feedback resistor network form a first-stage amplification network to convert the current signal output by the photodiode PIN5 into a voltage signal and realize primary amplification. Among them, the capacitor C76 is used to suppress high-frequency noise, and the resistance value of the feedback resistor network determines the primary gain. The second amplifier YF6D adopts a non-inverting amplifier structure, and the second resistor R148 and the third resistor R153 form a gain adjustment network to perform secondary amplification on the voltage signal after primary amplification. The second resistor R148 serves as an input impedance matching element, and the resistance value of the third resistor R153 determines the secondary gain. The photodiode PIN5 is connected in parallel to the input end of the first amplifier YF6C to eliminate the influence of dark current. The first resistor R146 can be a precision metal film resistor with a temperature coefficient of less than 50ppm / ℃ to ensure gain stability. The capacitor C76 may be a ceramic capacitor with a capacitance range of 1 pF to 100 pF. The second resistor R148 and the third resistor R153 may be chip-type thin-film fixed resistors with an accuracy of 0.1%.

[0041] A two-stage amplification structure achieves high-precision acquisition of weak optical signals. The first amplifier, YF6C, amplifies the weak signal output by photodiode PIN5, while the second amplifier, YF6D, provides secondary amplification. The capacitor in the feedback network effectively suppresses circuit noise, while the carefully selected resistors ensure gain stability. Compared to a single-stage amplification structure, this solution offers a wider dynamic range and better noise performance, adapting to inputs of varying optical signal intensities. By properly configuring the gain distribution of the two amplifier stages, signal quality can be maintained while avoiding output saturation.

[0042] Furthermore, the analog switch unit includes a front-stage selection analog switch and a plurality of rear-stage analog switches.

[0043] The front-stage selection analog switch is used to select different rear-stage analog switch paths, and each rear-stage analog switch has multiple gear settings.

[0044] Specifically, the pre-stage selection analog switch can be implemented using a multiplexer chip, such as an analog switch integrated circuit such as CD4051 or ADG708. The chip receives a logic signal from the control unit through a control pin, thereby turning on a specific channel. Furthermore, the post-stage analog switch can use a multi-channel single-pole multi-throw switch chip, such as a device such as MAX14759 or ADG1612. Each chip has multiple independent switch channels built in, and each channel corresponds to a feedback resistor with a different resistance value. As a preferred embodiment, the gear setting can be achieved by connecting a precision resistor network of different resistance values ​​in parallel, such as using an E96 series chip resistor combination with a resistance range of 1Ω to 1MΩ.

[0045] A hierarchical switching structure enables refined gain adjustment. The front-stage selector analog switch provides coarse adjustment, quickly switching the feedback network between different resistance ranges; the rear-stage analog switch provides fine adjustment, precisely matching the optimal resistance value within the selected range. This hierarchical control approach effectively solves the discontinuous adjustment problem of traditional variable gain systems while avoiding the increased control complexity caused by the excessive number of channels in a single switch structure.

[0046] Furthermore, the front-stage selection analog switch includes a first analog switch chip.

[0047] The first pin of the first analog switch chip inputs the first control signal Power_SEL1, the second pin is connected to an external voltage source, the third pin is grounded, the fifth pin is connected to the operational amplifier unit, and the fourth and sixth pins are connected to the subsequent analog switch. In this embodiment, the output end of the first amplifier YF6C in the operational amplifier unit is provided with a node INPUT_power5, and the fifth pin of the first analog switch chip is connected to the node INPUT_power5. The sixth pin outputs the first selection signal INPUT_SW1, and the fourth pin outputs the second selection signal INPUT_SW2.

[0048] Specifically, the first analog switch chip can be a general-purpose analog switch integrated circuit such as the CD4051 or ADG708. The second pin is connected to a +5V power supply, the third pin is grounded to form a reference potential, and the fifth pin serves as a signal output terminal connected to the feedback network of the operational amplifier. In a preferred embodiment, the enable terminal of the first analog switch chip can be connected to a chip select signal output by a control unit, and the address input terminal receives different high and low voltage levels to dynamically select different feedback resistor access paths in the subsequent analog switch.

[0049] Furthermore, the post-stage analog switch includes a first post-stage analog switch.

[0050] The first post-stage analog switch includes a second analog switch chip, a first pin of the second analog switch chip receives a second control signal Power_SEL2, a second pin is connected to an external voltage source, a third pin is grounded, and a fourth pin is connected in series with a fourth resistor R14, and then connected to one end of a fifth resistor R40 and a sixth resistor R41 respectively, and the other end of the fifth resistor R40 is grounded; the fifth pin is connected to the sixth pin of the first analog switch chip, that is, receiving the first selection signal INPUT_SW1; the sixth pin is connected to one end of a seventh resistor R19, and the other end of the seventh resistor R19 is connected to the other end of the sixth resistor R41, and the sixth resistor R41 and the seventh resistor R19 are connected to the inverting input end of the first amplifier YF6C in the operational amplifier unit.

[0051] Specifically, the fourth pin of the second analog switch chip forms a voltage divider network through the fourth resistor R14, and together with the fifth resistor R40 and the sixth resistor R41, constitutes an adjustable resistor network. The seventh resistor R19 is used to connect the other end of the sixth resistor R41 to the sixth pin to form a feedback path. The fourth pin and the sixth pin of the third analog switch chip are respectively connected to the eighth resistor R20 and the ninth resistor R23, and different gain adjustment gears are achieved through the combination of resistors. As a preferred embodiment, the resistance range of the fourth resistor R14 is 1kΩ to 10kΩ, the resistance ratio of the fifth resistor R40 and the sixth resistor R41 is 1:2 to 1:10, and the resistance of the seventh resistor R19 can be selected in the range of 1Ω-10kΩ or 10kΩ to 1MΩ according to the actual gain requirements. The resistance ratio of the eighth resistor R20 and the ninth resistor R23 is preferably 1:1 to 1:5 to achieve symmetrical gain adjustment characteristics.

[0052] In this embodiment, in the operational amplifier unit, a node INPUT_PIN is provided between the cathode of the photodiode PIN5 and the capacitor C76 , and the sixth resistor R41 and the seventh resistor R19 are connected to the node INPUT_PIN.

[0053] Furthermore, the post-stage analog switch further includes a second post-stage analog switch.

[0054] The second post-stage analog switch includes a third analog switch chip, a first pin of the third analog switch chip receives a third control signal Power_SEL3, a second pin is connected to an external voltage source, a third pin is grounded, a fourth pin is connected to one end of the eighth resistor R20, and a fifth pin is connected to the fourth pin of the first analog switch chip, that is, receiving the second selection signal INPUT_SW2; a sixth pin is connected to one end of the ninth resistor R23, the other end of the ninth resistor R23 is connected to the other end of the eighth resistor R20, and the eighth resistor R20 and the ninth resistor R23 are also connected to the inverting input end of the first amplifier in the operational amplifier unit.

[0055] In this embodiment, after the eighth resistor R20 and the ninth resistor R23 are connected, they are connected to the node INPUT_PIN, that is, connected to the inverting input terminal of the first amplifier YF6C, to form a complete first-stage amplifier circuit.

[0056] Specifically, the third analog switch chip adopts a dual-channel structure, wherein the fourth pin and the sixth pin form a parallel adjustable network through the eighth resistor R20 and the ninth resistor R23. As a preferred embodiment, the eighth resistor R20 and the ninth resistor R23 use metal film resistors with a precision of 1%, and the resistance range is designed to be 10kΩ to 1MΩ, thereby achieving fine adjustment of the gain gear. Furthermore, the third analog switch chip can use a low on-resistance analog switch such as ADG733, with a typical on-resistance of 2.5Ω, which helps to reduce signal path loss.

[0057] By adding a second post-stage analog switch to form a cascade structure with the first post-stage analog switch, the feedback network can combine to produce more equivalent resistance values. During operation, when the control unit detects that the output voltage of the operational amplifier is approaching the saturation threshold, it dynamically changes the connection method of the fourth resistor R14, the seventh resistor R19, the eighth resistor R20, and the ninth resistor R23 by switching the channel state of the second and third analog switch chips, thereby adjusting the closed-loop gain of the operational amplifier. This design effectively expands the dynamic range of the system and avoids the transient interference caused by traditional mechanical relay switching. At the same time, through the combined optimization of the resistor network, it achieves continuity and stability in gain adjustment.

[0058] Furthermore, the control unit is a microcontroller unit, and the microcontroller unit generates the control signal according to the amplitude of the amplified voltage signal Pin_ADC and a preset threshold.

[0059] The microcontroller unit can be implemented using a single-chip microcomputer or digital signal processor with analog-to-digital conversion capabilities, with an analog-to-digital conversion accuracy of no less than 12 bits recommended. The preset threshold can be stored in non-volatile memory and specifically divided into multiple voltage ranges, each corresponding to a different control signal output. The control signal can be output using a parallel digital signal or a serial communication protocol (such as I2C or SPI), and the signal transmission rate must meet the system's real-time requirements. As a preferred embodiment, the analog-to-digital conversion sampling frequency should be at least twice the signal bandwidth, and the voltage range division is recommended to use logarithmic spacing to accommodate the dynamic range characteristics of the optical signal.

[0060] By monitoring the amplitude of the amplified voltage signal Pin_ADC output by the operational amplifier in real time and digitally processing it in the microcontroller, a control signal is automatically generated to drive the analog switch unit to switch the feedback resistor when the signal noise is excessive or the sampling is saturated. This enables continuous adaptive gain adjustment, effectively avoiding the signal saturation and signal-to-noise ratio degradation problems that occur in traditional fixed-gain systems when the light intensity changes suddenly.

[0061] The above examples are used to illustrate the present invention, which are only used to help understand the present invention and are not intended to limit the present invention. Those skilled in the art of the present invention can make some simple deductions, modifications or substitutions based on the concept of the present invention.

Claims

1. A weak optical signal adaptive gain acquisition and amplification system based on analog switches, characterized in that: It includes a signal conversion unit, an operational amplifier unit, a control unit and an analog switch unit; The signal conversion unit is used to convert the optical signal into a current signal; the operational amplifier unit is connected to the signal conversion unit, receives and amplifies the current signal, and outputs an amplified voltage signal; The control unit is connected to the output end of the operational amplifier unit, receives the amplified voltage signal, and sends a control signal to the analog switch unit according to the amplified voltage signal; the analog switch unit connects resistors of different resistance values ​​to the feedback loop of the operational amplifier unit according to the control signal; The analog switch unit includes a front-stage selection analog switch and a plurality of rear-stage analog switches; The front-stage selection analog switch is used to select different rear-stage analog switch paths, and each rear-stage analog switch has multiple gear settings.

2. The weak optical signal adaptive gain acquisition and amplification system based on analog switch according to claim 1, characterized in that: The signal conversion unit is a photodiode.

3. The weak optical signal adaptive gain acquisition and amplification system based on analog switch according to claim 2, characterized in that: The operational amplifier unit includes a first amplifier and a second amplifier; The non-inverting input terminal of the first amplifier is connected to the positive electrode of the photodiode, the inverting input terminal of the first amplifier is connected to the negative electrode of the photodiode and one end of the capacitor respectively, and the other end of the capacitor and the output terminal of the first amplifier are connected to one end of the first resistor; The non-inverting input terminal of the second amplifier is connected to the first resistor, the inverting input terminal is connected in series with the second resistor and then grounded, and a third resistor is connected in parallel between the output terminal and the inverting input terminal of the second amplifier.

4. The weak optical signal adaptive gain acquisition and amplification system based on analog switches according to claim 1, characterized in that: The front-stage selection analog switch includes a first analog switch chip; The first pin of the first analog switch chip receives a first control signal, the second pin is connected to an external voltage source, the third pin is grounded, the fifth pin is connected to the operational amplifier unit, and the fourth and sixth pins are connected to the subsequent analog switch.

5. The weak optical signal adaptive gain acquisition and amplification system based on analog switch according to claim 4, characterized in that: The post-stage analog switch includes a first post-stage analog switch; The first post-stage analog switch includes a second analog switch chip, wherein a first pin of the second analog switch chip receives a second control signal, a second pin is connected to an external voltage source, a third pin is grounded, a fourth pin is connected in series with a fourth resistor, and then connected to one end of a fifth resistor and one end of a sixth resistor respectively, and the other end of the fifth resistor is grounded; the fifth pin is connected to the sixth pin of the first analog switch chip; the sixth pin is connected to one end of a seventh resistor, and the other end of the seventh resistor is connected to the other end of the sixth resistor, and the inverting input terminal of the first amplifier in the operational amplifier unit is connected between the sixth and seventh resistors.

6. The weak optical signal adaptive gain acquisition and amplification system based on analog switches according to claim 5, characterized in that: The post-stage analog switch further includes a second post-stage analog switch; The second post-stage analog switch includes a third analog switch chip, a first pin of the third analog switch chip receives a third control signal, a second pin is connected to an external voltage source, a third pin is grounded, a fourth pin is connected to one end of an eighth resistor, a fifth pin is connected to the fourth pin of the first analog switch chip, a sixth pin is connected to one end of a ninth resistor, the other end of the ninth resistor is connected to the other end of the eighth resistor, and the eighth resistor and the ninth resistor are further connected to the inverting input end of the first amplifier in the operational amplifier unit.

7. The weak optical signal adaptive gain acquisition and amplification system based on analog switches according to claim 1, characterized in that: The control unit is a microcontroller unit, and the microcontroller unit generates the control signal according to the amplitude of the amplified voltage signal and a preset threshold.

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