64 results about "Common-mode rejection ratio" patented technology

The invention relates to the technical field of chip detection, and discloses a high-reliability power supply chip circuit fault detection system, which comprises a built-in self-test architecture integrated in a low dropout regulator chip, and the built-in self-test architecture is provided with a first test mode and a second test mode which are switched based on a mode switching control circuit. The detection module is used for detecting key performance parameters of an error amplifier sub-circuit in a low dropout linear regulator chip, the detection module is used for measuring the direct current loop gain, the offset voltage, the common mode rejection ratio and the power supply ripple rejection ratio of the amplifier in the first test mode, and the detection module is used for measuring the unity gain bandwidth of the amplifier in the second test mode. According to the invention, through the design of a built-in self-test architecture and two test modes, abnormal states such as differential circuit imbalance and feedback loop fault can be identified in a bare chip stage, chips with poor performance are rejected in advance, and the LDO chip is ensured to reach a ppb-magnitude high reliability standard.

According to the electroencephalogram signal collecting device and method, the common-mode rejection ratio is increased through the right leg driving module, high-frequency noise and low-frequency noise are filtered out through the band-pass filtering module, power frequency interference is eliminated through the notch module, and filtering processing is conducted on the power frequency interference and the power frequency multiple in a software mode through the power frequency filtering model; therefore, the radio frequency interference is improved, the anti-interference capability of electroencephalogram signal acquisition is greatly improved, and the accuracy and stability of electroencephalogram signal acquisition are improved.

The invention relates to the technical field of industrial automation control, in particular to a full-isolation data acquisition method, circuit and terminal. The acquisition method comprises the following steps: acquiring a non-electric-quantity analog signal through a sensor, and preprocessing the analog signal, including low-pass filtering, common-mode noise suppression and gain programmable amplification. Through the designed Flyback-PFM / PWM hybrid modulation isolation power supply, four paths of mutually isolated low ripple output (the ripple suppression ratio reaches 60dB at 100kHz) are realized under the wide voltage input condition of 8-36V, and a secondary side feedback network is combined with a pi-type filter circuit to effectively suppress the interference of high-frequency switching noise on the reference voltage of a sigma-delta type ADC (Analog to Digital Converter). And the common-mode rejection ratio of the signal conditioning module is improved to 120dB.

The invention discloses a surface diaphragm electric signal acquisition system, which adopts a processor and integrates a metal dry electrode and an acquisition front end to realize high-integration-level non-invasive diaphragm electric signal acquisition. The acquisition front end comprises a signal front end amplification circuit which is constructed by an LM324 chip and an LM358 chip, has the characteristics of high common-mode rejection ratio and low power consumption, and ensures stable amplification and anti-interference capability of weak signals. The lower computer takes STM32F407VET6 as a core, adopts multi-channel ADC sampling, and combines timer control and a DMA transmission mechanism to realize high-real-time and high-stability signal acquisition. The upper computer is developed based on a QT framework and has the functions of real-time display, storage and signal processing. The system has the advantages of high real-time performance, high acquisition precision, low interference and the like, and can provide efficient and reliable technical support for respiration synchronous analysis and clinical medical diagnosis.

A measurement circuit including a power supply, a load output terminal connected to the power supply and connected to a system ground via a load, an amplifier comprising power terminals connected to the power supply, and an output terminal connected to the system ground via a measurement resistor, the amplifier is configured to supply current from the power supply to the load via the measurement resistor and the system ground producing a voltage across the measurement resistor that corresponds to the supply current through the load.

The application discloses to the technical field of differential amplifier, specifically a differential amplifier circuit with high common-mode input voltage, comprising: an internal differential amplification circuit for processing input signals; a power supply voltage detection module for detecting an external power supply voltage for powering the circuit and outputting a detection signal; a charge pump module for boosting the external power supply voltage to generate a boosted power supply; a control module coupled with the power supply voltage detection module and the charge pump module respectively for receiving the detection signal and controlling the working state of the charge pump module based on the detection signal; based on this, the application has the effect of enabling the chip to maintain high common-mode input voltage processing capability and high common-mode rejection ratio within the full power supply voltage range, and can stably process high common-mode signals without relying on a specific numerical high-voltage power supply, solving the problem of sharp performance decay under low power supply voltage in the prior art.

The embodiment of the invention discloses a buffer circuit. The buffer circuit comprises a capacitor module and a follower module, wherein one end of the capacitor module inputs a first voltage, the other end of the capacitor module is electrically connected with a first input end of the follower module, a second input end of the follower module inputs a target signal, a power supply end of the follower module inputs a second voltage, and a first output end and a second output end of the follower module respectively output two signals; the capacitor module comprises a capacitor and a switch unit, and the capacitance value of the capacitor module is adjustable. According to the buffer circuit provided by the embodiment of the invention, the power supply rejection ratio of the buffer circuit and the input common-mode rejection ratio can be improved.

This invention discloses a shunt amplifier and electronic device. By introducing at least one resistor adjustment unit, and defining its connection to at least one resistor branch in a first resistor network and / or a second resistor network, it adjusts the equivalent resistance value of the connected branch. This allows the equivalent resistance value of the resistor branch to be adjusted after circuit molding, thereby compensating for proportional resistor mismatch caused by process deviations and directly solving the proportional resistor mismatch problem caused by process deviations. This invention enables the adjustment unit to actively compensate for the corresponding resistor branch without changing the overall circuit architecture, correcting mismatch errors and improving resistor matching accuracy. Since the common-mode rejection ratio (CMRR) of a shunt amplifier is highly dependent on the accuracy of the resistor ratio, improving resistor matching accuracy directly optimizes the CMRR, enhances the amplifier's robustness to process fluctuations, and makes its performance more stable in high-precision, high-complexity applications.

The invention discloses a differential capacitance MEMS (Micro Electro Mechanical System) acceleration sensor with a high common mode rejection ratio and a preparation method of the differential capacitance MEMS acceleration sensor. The sensor adopts a symmetrical double-beam and double-mass-block structure, acceleration measurement is realized through symmetrical layout of three-axis detection comb tooth capacitors, and the three-axis detection comb tooth capacitors specifically comprise X-axis and Y-axis differential detection comb tooth capacitor pairs and Z-axis detection comb tooth capacitors; the X-axis differential comb tooth capacitor pair and the Y-axis differential comb tooth capacitor pair take the central axis of the double-beam double-mass-block structure as the symmetry axis, and two groups of capacitors are arranged, so that under the action of acceleration, the overlapping areas of movable comb teeth and fixed comb teeth of the X-axis differential comb tooth capacitor pair and the Y-axis differential comb tooth capacitor pair are changed in an opposite trend, and differential output is formed; the acceleration is measured by detecting the change of the differential capacitance, and common-mode interference is effectively suppressed by using a differential superposition signal processing mode, so that high signal-to-noise ratio and long-term stability are ensured; the sensor is prepared by adopting a semiconductor process and an MEMS (Micro-Electro-Mechanical System) technology, so that wafer-level manufacturing is realized, and the consistency and batch production of chips are guaranteed.

The utility model discloses a medical electrical equipment common mode rejection ratio testing device, the input end of which is connected with a signal generator, and the output end of which is connected with electrical equipment to be tested. The circuit board is mounted in the shielding shell; one side surface of the shielding shell is provided with a first connecting hole for connecting a first connecting wire, and the other side surface of the shielding shell is provided with a plurality of second connecting holes for connecting a plurality of second connecting wires; a protective grounding terminal is arranged at the bottom of the shielding shell, the shielding shell is connected inside the protective grounding terminal, and a connecting end is provided outside the protective grounding terminal; the connection between the testing device and the signal generator is realized through the first connecting wire, and the connection between the testing device and the electrical equipment to be tested is realized through the plurality of second connecting wires. The testing device is provided with the shielding shell, pickup of unwanted external noise can be effectively reduced, and in order to better exert shielding effectiveness, the shielding shell is provided with the protection grounding terminal, and complete grounding protection can be provided for equipment.

The present invention discloses an operational amplifier input circuit and a method for dynamically adjusting the substrate voltage of the operational amplifier input circuit. The operational amplifier input circuit includes an input stage unit, a substrate bias unit, and a substrate voltage adjustment unit. The input stage unit includes a first differential transistor pair; the substrate bias unit includes a second differential transistor pair and a resistor unit, the resistor unit being configured to output a substrate voltage provided to the first differential transistor pair; and the substrate voltage adjustment unit adjusts the substrate voltage based on changes in the input common-mode voltage. According to the operational amplifier input circuit of the present invention, the substrate voltage of the first differential transistor pair of the input stage unit is set by the substrate bias unit, and the substrate voltage adjustment unit adjusts the substrate voltage when the input common-mode voltage varies over a wide range, thereby providing the input stage unit with a better operating point and improving the circuit's performance indicators, such as the common-mode rejection ratio, at low and high common-mode voltages.

The application relates to the chip detection technical field and discloses a high-reliability power supply chip circuit fault detection system which comprises a built-in self-test architecture integrated in a low-dropout linear voltage regulator chip. The built-in self-test architecture is provided with a first test mode and a second test mode which are switched based on a mode switching control circuit to detect the key performance parameters of an error amplifier subcircuit in the low-dropout linear voltage regulator chip. The first test mode is used for measuring the direct current loop gain, the offset voltage, the common mode rejection ratio and the power supply ripple rejection ratio of the error amplifier. The second test mode is used for measuring the unit gain bandwidth of the error amplifier. According to the built-in self-test architecture and the two test modes, the application can identify abnormal states such as differential circuit imbalance and feedback loop failure in the bare chip stage, and can remove the chips with poor performance in advance, so that the LDO chip can reach the high-reliability standard of ppb.

The utility model relates to the technical field of industrial automation control, in particular to a fully-isolated data acquisition circuit. The data acquisition circuit comprises an isolation power supply module which is used for converting 8-36V DC input voltage into four paths of mutually isolated low-ripple output power supplies and respectively supplying power to a sensor signal conditioning circuit, a microcontroller module, a communication interface module and an analog transmitting module. According to the utility model, through the designed Flyback-PFM / PWM hybrid modulation isolation power supply, four paths of mutually isolated low ripple output (the ripple suppression ratio reaches 60dB at 100kHz) are realized under the wide voltage input condition of 8-36V, and a secondary side feedback network is combined with a Pi-type filter circuit to effectively suppress the interference of high-frequency switching noise on the reference voltage of the sigma-delta ADC. And the common-mode rejection ratio of the signal conditioning module is improved to 120dB.

The invention relates to the technical field of high-voltage direct-current power transmission, and discloses a high-voltage direct-current converter valve cooling system flow sensor anti-interference circuit design method, which comprises the following steps: constructing a three-stage collaborative anti-interference system: a front-stage signal acquisition and primary protection circuit, a common-mode choke, a TVS diode and a PPTC resettable fuse combined network, and a high-voltage direct-current converter valve cooling system flow sensor anti-interference circuit; common-mode rejection and transient overvoltage protection are carried out on the original differential signals; the intermediate signal conditioning and isolating circuit is used for realizing accurate amplification of signals, thorough cut-off of ground loop interference and deep filtering through an instrument amplifier with a high common mode rejection ratio, an isolating amplifier and a second-order active Butterworth low-pass filter in sequence; the post-stage power supply anti-interference circuit provides a clean and stable power supply for the system through the cascade design of a pi-type filter, an isolation DC-DC, a magnetic bead isolation network and an ultra-low noise linear voltage regulator. According to the invention, through the full-link and multi-layer collaborative design, the anti-interference capability, the measurement precision and the operation reliability of the sensor in an extreme electromagnetic environment are improved.

The present application relates to a kind of earphone type brain electricity collection front-end anti-interference system, including electrode acquisition unit, static electricity protection unit, front-end pollution suppression unit, input anti-interference filter unit, analog front-end acquisition unit, common mode feedback / bias drive unit, power supply and reference stable unit, common ground layout unit, interference monitoring unit and anti-interference control unit.The earphone type brain electricity collection front-end anti-interference system, method, device, processor and its computer readable storage medium of the present application are used, the interference of two different sources of transient impact and chronic leakage can be more accurately governed, the common mode rejection ratio can be improved, baseline drift caused by wearing state change, high impedance contact and human coupling can be reduced, overall noise can be reduced, and data stability and availability can be improved in brain electricity collection and wireless communication concurrent scene.

The invention discloses a substrate integrated suspended strip line self-packaging type non-reflection differential filtering power divider with a broadband common-mode absorption characteristic, and relates to the technical field of radio frequency. The power divider comprises a first packaging layer, a first air cavity layer, a circuit layer, a second air cavity layer and a second packaging layer. The first packaging layer comprises a first substrate, and metal layers are arranged on the two end faces, in the first direction, of the first substrate. The second packaging layer comprises a fifth substrate, and metal layers are arranged at the two ends of the fifth substrate in the first direction. The first packaging layer, the first air cavity layer, the circuit layer, the second air cavity layer and the second packaging layer are sequentially stacked in the first direction. By arranging the first packaging layer and the second packaging layer, a self-packaging structure can be formed, external electromagnetic interference and internal signal leakage can be suppressed, a complete and stable grounding layer can be provided, the common-mode rejection ratio can be improved, electromagnetic isolation with other modules can be realized, crosstalk can be reduced, and the anti-interference capability can be remarkably improved.

The utility model relates to the related field of circuit design, in particular to a circuit for controlling the voltage scaling ratio of an operational amplifier by using a relay. According to the utility model, through the OP07CP operational amplifier, the offset voltage drift voltage of the OP07CP operational amplifier is very small by utilizing the low offset voltage characteristic of the OP07CP operational amplifier, errors caused by offset voltage introduction are avoided, the precision is high, the noise is low, the common-mode rejection ratio is high, the power supply voltage range is wide, small signals can be amplified and processed more accurately, and the power supply voltage range is wide. Moreover, the voltage scaling ratio of the circuit can be dynamically adjusted, the design allows the circuit to adapt to various input signal ranges, and the universality and flexibility of the system are improved.

The invention provides a short wave infrared pixel readout circuit and a control method thereof, the short wave infrared pixel readout circuit converts an optical signal into a light current based on a photoelectric conversion module, and provides a preset transconductance gain through a symmetric differential amplification structure in a charge integration amplification module, so as to amplify the light current based on the preset transconductance gain; charge integration is carried out on the light current to obtain integral voltage; and performing reset sampling and signal sampling on the integral voltage through the correlated double-sampling module to obtain a sampling voltage. The short-wave infrared pixel reading circuit provided by the invention adopts a symmetrical differential amplification input structure, has a relatively high common-mode rejection ratio and a relatively good anti-interference capability, and improves the anti-interference capability in an amplification process under the condition of not increasing power consumption; the correlated double sampling modules are concentrated in the reading circuit, signals are not transmitted for multiple times between pixels and a column-level circuit, the processing pressure of the column-level circuit is reduced, the number of circuit switches is small, time sequence control is simple, and the pixel area is reduced.

The embodiment of the invention provides a programmable gain instrumentation amplifier used in the field of sensing detection. The programmable gain network is applied to the technical field of integrated circuits and comprises a low-pass filtering module, a chopping amplification module, a first programmable gain network, a second programmable gain network and a buffer amplification module, the low-pass filtering module is used for receiving an input differential signal, filtering the differential signal and outputting a filtered signal; the chopping amplification module is used for carrying out chopping processing on the filtering signal and outputting a chopping signal; the first programmable gain network is used for performing first gain adjustment on the chopping signal and outputting a first gain adjustment signal; the second programmable gain network is used for performing second gain adjustment on the first gain adjustment signal and outputting a second gain adjustment signal; and the buffer amplification module is used for processing the second gain adjustment signal to obtain an output signal. The amplifier has the characteristics of low noise and high common-mode rejection ratio, and is suitable for detecting, amplifying and processing high-precision signals.

Semiconductor devices and methods of manufacturing a balun having improved common mode rejection ratio. An electronic device has a first transformer and a second transformer. A first winding of the first transformer is coupled to a first winding of the second transformer by an interconnect transmission line. A phase compensation transmission line is coupled to a second winding of the first transformer. The phase compensation transmission line is configured to match an impedance of the interconnect transmission line.

The invention relates to a wireless circuit with an isolated active combiner. In particular, an electronic device may include a wireless circuit having a first transmission line and a second transmission line. A signal combiner may couple the first transmission line and the second transmission line to a path. The combiner may include an output circuit coupled to the path, a first transistor coupling the first transmission line to a first input of the output circuit, and a second transistor coupling the second transmission line to a second input of the output circuit. The signal combiner may include a first capacitor coupling the first transmission line to the second input, and may include a second capacitor coupling the second transmission line to the first input. A resistor may be coupled in parallel with the capacitors if desired. The output circuit can show a high common mode rejection ratio. The output circuit, the capacitors, and / or the resistors may neutralize parasitic components of the transistors.

The invention relates to a fully differential chopping amplification circuit and a self-trimming method thereof, an analog switch switches an input signal between a trimming mode and a measurement mode, a common-mode calibration signal Vcal is accessed in the trimming mode to realize CMRR self-trimming, and a differential signal Vin to be measured is accessed in the measurement mode to realize signal acquisition; the differential input BUFER receives a common-mode calibration signal Vcal in a trimming mode, receives a differential signal Vin to be measured in a measurement mode, and buffers a corresponding input signal; the P-end conditioning circuit performs low 1 / f noise suppression, gain optimization and common-mode interference suppression on the buffered input signal; the N-end conditioning circuit performs low noise suppression, gain matching and common-mode interference suppression on the buffered signal; the ADC module converts the received differential signal into a digital signal in a trimming mode, converts the received differential signal into a digital signal in a measuring mode, and outputs the digital signal to a rear-end processing unit to complete signal acquisition and conversion. Common-mode rejection ratio trimming of the fully differential circuit is realized, and the common-mode rejection ratio of the circuit is improved.

The present invention provides a double-ended output circuit and a signal processing circuit based on a single-ended signal source, in which the signal processing circuit based on the single-ended signal source is configured to amplify an original signal in a single-ended signal form output by the single-ended signal source with an instrumentation amplifier (In-Amp), so as to utilize the high input impedance of the instrumentation amplifier and improve the signal processing efficiency. Complete and high-precision amplification processing is carried out on an original signal in a single-ended signal form output by the single-ended signal source by virtue of the native advantages of high common-mode rejection ratio, high gain adjustment precision, low temperature drift, good linearity and low noise; therefore, weak signals in original signals output by the single-ended signal source can be effectively captured, and the reliability of a corresponding sensing device adopting the signal processing circuit based on the single-ended signal source is guaranteed correspondingly when the single-ended signal source is a corresponding sensing device.

This invention relates to the field of analog front-end technology and discloses a multi-channel high common-mode rejection ratio (CMRR) signal acquisition system based on idle-phase common-mode cancellation technology. The system includes: a multi-channel presampler based on a floating dynamic operational amplifier and idle-phase common-mode cancellation technology, used to sample weak input signals. Simultaneously, the output signal is periodically short-circuited during idle phases at the presampler's output to eliminate common-mode signals and improve the CMRR; a multi-channel noise-shaping successive approximation analog-to-digital converter (ADC), which takes the weak signal acquired by the presampler as input and outputs a digital signal; and an ADC that provides a time-division multiplexed clock to drive the presampler, achieving phase-synchronized clock control. The presampler technology based on idle-phase common-mode cancellation proposed in this invention has advantages such as low power consumption and high CMRR, and is suitable for low-gain multi-channel neural signal acquisition systems, effectively eliminating common-mode interference during neural signal acquisition.

The application discloses a six-port single-ended differential switching quadrature hybrid coupler, which is used for realizing mutual conversion of single-ended signals and quadrature differential signals and mutual conversion of differential signals and quadrature single-ended signals as a single device; when used for mutual conversion of single-ended signals and quadrature differential signals, a first port is a single-ended input port, a sixth port is a single-ended isolation port, a second port and a third port are I-path differential output ports, and a fourth port and a fifth port are Q-path differential output ports; when used for mutual conversion of differential signals and quadrature single-ended signals, the second port and the third port are differential input ports, the first port and the sixth port are I-path and Q-path outputs respectively, and the fourth port and the fifth port are differential isolation ports. Compared with a traditional quadrature hybrid coupler, the application reduces circuit area and cost, preferably adopts an on-chip transformer and a capacitor to form a lumped circuit, has a good common-mode rejection ratio, and is suitable for applications such as a Doherty power amplifier and a vector modulation phase shifter.

The invention discloses a differential sampling common mode error compensation method and circuit, the circuit comprises a resistor, a differential amplification module, a voltage following module, a multi-channel synchronous sampling ADC module and a calibration module, the differential amplification module and the resistor form a differential amplification circuit; the multi-channel synchronous sampling ADC module receives input signals of a first sampling voltage V1 and a second sampling voltage V2 and outputs Vout, the voltage following module receives input signals of any sampling voltage of a differential sampling input end and outputs V1out, the multi-channel synchronous sampling ADC module synchronously collects the Vout and the V1out and outputs two voltage code values respectively, the calibration module calibrates the voltage code values to obtain Vcode, and the Vcode outputs the first sampling voltage V1 and the second sampling voltage V2. And suppression of the common-mode signal is realized. The multi-channel synchronous sampling ADC module is arranged, so that the time sequence consistency of multi-channel signal acquisition is ensured, and an instantaneous value also has a common-mode rejection ratio during high-speed sampling.

The invention discloses a high-precision electrochemical detection system and a detection method. The system comprises a front-end circuit, a middle-end circuit and a rear-end loop, a front-end circuit converts a working electrode weak current into a voltage signal through a trans-impedance amplifier, and then the voltage signal is processed by a fully differential amplifier with a high common-mode rejection ratio; the middle-end circuit generates an adjustable bias voltage and applies the adjustable bias voltage to the other input end of the fully differential amplifier so as to compensate the offset voltage and realize single-end-to-differential conversion; the rear-end loop is used for stabilizing the potential of the reference electrode, collecting potential data in real time through the monitoring circuit, processing the potential data by the main control module, sending out a control instruction, and finally dynamically adjusting an excitation signal through the analog excitation circuit to form a stable closed loop. The invention has the advantages of high measurement precision, strong stability and strong anti-interference capability, is suitable for reliable detection of trace substances, and solves the problems of insufficient output voltage stability, low signal-to-noise ratio and susceptibility to ambient temperature interference of the existing electrochemical detection equipment in low-concentration sample detection.

The utility model belongs to the technical field of industrial automation measurement and control, and discloses an isolation type thermal resistance temperature signal conditioning system, which comprises a constant current source circuit; an amplification circuit; a VF conversion circuit; an FV conversion circuit; a low-pass filter circuit; and a linearization circuit. According to the utility model, the instrument amplifier with a high common-mode rejection ratio is adopted to suppress common-mode noise, the hardware filtering design is optimized, multi-stage low-pass filtering is adopted to eliminate power frequency harmonic waves, and a mirror image constant current source is adopted to enhance the stability; a reverse protection circuit is added in a double-TVS diode clamping mode, and a wide input voltage range power supply chip is properly selected. VF / FV conversion time sequence control is adopted, a scheme of dynamically adjusting cut-off frequency is adopted, filtering parameters are automatically switched according to a signal variable rate, and noise suppression and response speed are balanced.

The invention discloses a gate charge measuring method and device for an MOSFET (Metal-Oxide-Semiconductor Field Effect Transistor) device, and relates to the technical field of power electronic test and measurement. The first end of the load module is electrically connected with the drain electrode of the tested power device, and the second end of the load module is electrically connected with the first end of the bus capacitor; the gate driving module is electrically connected between the gate and the source of the tested power device, and the source of the tested power device is electrically connected with the second end of the bus capacitor; the gate driving module comprises a driving resistor; the high-voltage differential voltage probe is electrically connected to two ends of a drain electrode and a source electrode of a tested power device, the low-voltage differential probe with the high common-mode rejection ratio is electrically connected to two ends of the driving resistor, and the low-voltage differential voltage probe is electrically connected to two ends of a grid electrode and the source electrode of the tested power device; and the current probe is electrically connected to a test loop formed between the source electrode of the tested power device and the second end of the bus capacitor. According to the invention, the gate charge measurement accuracy is obviously improved.

The invention provides an anti-interference non-contact temperature measurement method for a dual-wavelength light intensity ratio up-conversion material, and relates to the technical field of non-contact temperature measurement. According to the method, Ho < 3 + > / Yb < 3 + > NaYF4 fluorescent powder is used as a temperature sensitive medium, and 540nm and 640nm dual-band visible light is generated through 980nm laser non-contact excitation; the fluorescence intensity ratio of two wavelengths is synchronously obtained by utilizing a narrow-band optical filter-double photoelectric detector-differential amplification link, and wide-temperature-zone temperature measurement with the precision of + / -1.5 DEG C and the response time of less than 3s is realized within the measurement distance of 5-20cm by combining a TCLs + NTCLs double-strategy temperature model. The particle size of the core-shell particles prepared through the solvothermal method is 175-200 nm, the common-mode rejection ratio of a differential amplification circuit is larger than or equal to 80 dB, and laser fluctuation and ambient light interference are effectively eliminated. The system works with a 3.3 V single power supply, the power consumption is less than 310mW, the temperature drift is less than 10ppm / DEG C, the structure is compact, an intelligent monitoring terminal is easy to embed, and the system is suitable for complex scenes such as high-reflection surfaces and strong electromagnetic interference.