A low-noise operational amplifier frequency compensation system

Abstract

The application discloses a kind of based on low noise operational amplifier frequency compensation system, it is related to analog circuit frequency domain modeling and stability optimization technical field, by obtaining the unit gain frequency of operational amplifier, maximum phase lag angle and low-frequency cut-off point;Frequency compensation parameter group is constructed, and initial frequency domain stability model is established based on open-loop transfer function;Compensation parameter group is sequentially imported into model, and frequency scanning simulation is carried out, and the phase response value under each compensation configuration is extracted, and stability function is constructed and is marked with label;Further filter out the compensation parameter that meets stability requirement and the minimum reactance amplitude, feedback for frequency compensation loop adjustment;The application realizes the fine modeling and optimization selection of frequency compensation strategy, improves the stability and efficiency of system in low noise, high-precision application, with good engineering applicability.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of analog circuit frequency domain modeling and stability optimization, and particularly relates to a frequency compensation system based on a low-noise operational amplifier. BACKGROUND

[0002] With the wide application of precision sensors and high-speed data acquisition systems in medical monitoring, aerospace and quantum measurement fields, the system has put forward very high requirements on the performance of low-noise operational amplifiers in the analog signal processing link. Especially in the low-frequency band (<10Hz) weak signal amplification scene, the traditional operational amplifier has problems such as frequency compensation mismatch, open-loop gain drop and insufficient phase margin, which leads to the problems of the whole system such as increased zero drift, high-frequency output noise and even closed-loop oscillation, and seriously affects the signal accuracy and system stability.

[0003] The current common frequency compensation method (such as Miller compensation) can provide basic phase margin in the medium frequency band, but it has the following difficult problems to solve at very low frequency signals (<1Hz):

[0004] The compensation capacitor value must be very large to maintain stability, which leads to a significant increase in chip area; the very low frequency compensation capacitor cannot realize frequency self-adaptation, which leads to response delay of the amplifier when the signal jumps;

[0005] The coupling effect of the multi-stage compensation structure leads to the frequency drift of the noise floor, causing the low-frequency resonance point of the system to shift to the working bandwidth. Especially in the low-temperature, high-magnetic, high-impedance measurement scene, the frequency compensation instability problem of this kind is more significant, which directly threatens the accuracy index of the system to meet the standard and the long-term working reliability. SUMMARY

[0006] The purpose of the present application is to provide a frequency compensation system based on a low-noise operational amplifier to solve the problems in the background art.

[0007] In order to achieve the above purpose, the present application provides the following technical scheme: a frequency compensation system based on a low-noise operational amplifier, comprising:

[0008] A frequency characteristic extraction module: obtaining the open-loop gain and phase response curve of the target low-noise operational amplifier at different frequency points, and extracting the low-frequency cutoff point ω1, the unity gain frequency ωu and the maximum phase lag θm;

[0009] A compensation parameter construction module: constructing a frequency compensation parameter group P={P1, P2,..., Pn}, wherein Pi={Ci, Ri}, Ci is the compensation capacitor value, Ri is the equivalent compensation resistance value, and Pn is the maximum compensation capacitance and resistance range;

[0010] The frequency domain stability modeling module: based on the obtained ω1, ωu and θm characteristics, an initial frequency domain stability model M0 is constructed, specifically including: taking the unity gain frequency, the maximum phase lag angle and the low frequency cutoff point as the input boundary conditions, defining the target phase response curve and the open loop gain envelope line in the frequency range; establishing an open loop transfer function model wherein ω1 is the low frequency pole frequency, ωz is the compensation zero frequency, A is the low frequency gain constant, and s is the independent variable in the complex frequency domain; the coupling relationship between the open loop transfer function model and each compensation parameter unit in the compensation parameter group is established to form a frequency response mapping model; the initial frequency domain stability model M0 is defined as a response function set containing the frequency response mapping relationship;

[0011] The frequency scanning simulation module: the frequency compensation parameter group P is sequentially introduced into the initial frequency domain stability model M0, and the stability function F(Pi) under each compensation configuration is obtained through frequency scanning simulation, and each group Pi is marked whether it meets the stability critical condition F(Pi)≥Φ0, wherein Φ0 is the preset minimum phase margin;

[0012] The optimal compensation extraction module: according to the F(Pi) marking result, the minimum compensation parameter set P* that meets the stability requirement is extracted, and P* is fed back to adjust the frequency compensation link of the original amplifier, specifically including: from the compensation parameter units that have been given the qualified mark, the parameter set whose stability function value is greater than zero is selected; based on the preset optimization target, the reactance amplitude composed of the compensation capacitance value and the equivalent compensation resistance value is taken as the evaluation index, and the total equivalent reactance of each parameter unit is calculated; under the condition of meeting the non-negative stability function value, the parameter unit with the minimum reactance amplitude is extracted from the screening result to form the minimum compensation parameter set; the minimum compensation parameter set is fed back to adjust the frequency compensation loop structure of the original amplifier.

[0013] Preferably, the frequency characteristic extraction module includes: performing open loop connection test on the low noise operational amplifier to obtain the open loop gain and phase response data curves in the preset frequency scanning range; performing feature point extraction processing on the obtained frequency response curve to identify the unity gain frequency ωu corresponding to the first time when the open loop gain drops to 0dB; using a third order curve fitting method to fit the phase response data, calculating the phase angle corresponding to the unity gain frequency, and determining the maximum phase lag θm; based on the gain-frequency response slope variation law, the inflection point position is detected by using the derivative method, so as to extract the corresponding low frequency cutoff point ω1.

[0014] Preferably, the compensation parameter construction module comprises: determining a value range of the compensation capacitance value based on the pre-measured unit gain frequency, the maximum phase lag angle and the low frequency cut-off point frequency of the low noise operational amplifier, the lower limit of which is defined by the minimum phase margin requirement, and the upper limit of which is defined by the DC stability condition; generating a plurality of compensation capacitance values in the value range of the compensation capacitance value according to a preset incremental step, and analytically calculating the equivalent compensation resistance value corresponding to each compensation capacitance value based on the equivalent small signal model, so that the two form a one-to-one parameter pair; combining each compensation capacitance value and the corresponding equivalent compensation resistance value to form a compensation parameter unit Pi={Ci, Ri}, Ci is the compensation capacitance value, Ri is the equivalent compensation resistance value, and Pn is the maximum compensation reactance range; sorting all compensation parameter units according to the reactance amplitude formed by the compensation capacitance value and the equivalent compensation resistance value, and defining the compensation parameter unit with the largest reactance amplitude as the maximum compensation reactance range to construct a complete frequency compensation parameter group P.

[0015] Preferably, the frequency scanning simulation module comprises: substituting each compensation parameter unit in the frequency compensation parameter group into the initial frequency domain stability model in turn to generate the corresponding frequency response function; performing numerical simulation on each frequency response function in a set frequency scanning range to extract the phase response value at the unit gain frequency; comparing the extracted phase response value with the preset minimum phase margin threshold to construct a stability function , wherein is the phase response corresponding to the compensation parameter unit; determining whether each stability function value is greater than or equal to zero, and labeling each group of compensation parameter units according to the determination result to distinguish between those that meet the stability requirement and those that do not.

[0016] Preferably, determining whether each stability function value is greater than or equal to zero, and labeling each group of compensation parameter units according to the determination result, comprises: numerically determining the stability function value corresponding to each compensation parameter unit in the frequency scanning simulation result, if the function value is greater than or equal to zero, it is considered to meet the stability requirement; giving a qualified identification to the compensation parameter unit that meets the determination condition, and giving an unqualified identification to the compensation parameter unit that does not meet the determination condition; uniformly arranging all the labeled compensation parameter units into a structured labeling result set, which contains the compensation capacitance value, the compensation resistance value, the stability function value and the corresponding label; sorting the qualified identification units in ascending or descending order according to the stability function value.

[0017] In the technical scheme, the technical effects and advantages provided by the application are as follows: the frequency compensation method based on the low-noise operational amplifier provided by the application fully utilizes frequency domain characteristic parameters, including unit gain frequency, maximum phase lag angle and low frequency cutoff point, realizes quantitative evaluation of phase margin and stability function mapping of compensation configuration effect by constructing an initial frequency domain stability model and combining frequency compensation parameter groups for frequency scanning simulation. The method can efficiently screen compensation parameter units meeting the phase margin constraint through stability function value judgment and label marking mechanism, ensures that the system maintains sufficient stability margin under different compensation conditions, and avoids the uncertainty caused by experience-based parameter selection in traditional design.

[0018] In addition, the application adopts a minimum capacitance resistance optimization strategy, extracts a compensation parameter group with minimum resource occupation in a capacitor-resistor combination under the premise of ensuring stability requirements, and feeds back the compensation parameter group to an actual frequency compensation link of the operational amplifier, thereby significantly improving compensation efficiency and resource utilization. The technical scheme has modeling accuracy and implementability, is suitable for low-frequency signal amplification, high-precision analog-to-digital conversion, electrophysiological signal detection and other scenes with high requirements for low noise and frequency stability, and reduces power consumption, area and device complexity while ensuring stable operation of the system. BRIEF DESCRIPTION OF DRAWINGS

[0019] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed in the embodiments will be briefly introduced. Obviously, the drawings described below are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art based on these drawings.

[0020] Figure 1 The system module flowchart of the present application. DETAILED DESCRIPTION

[0021] In order to make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical scheme in the embodiments of the present application will be described clearly and completely in combination with the drawings in the embodiments of the present application. Obviously, the described embodiments are some embodiments of the present application, not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0022] Embodiment, please refer to Figure 1 As shown in the drawings, the low-noise operational amplifier frequency compensation system described in the embodiments includes:

[0023] Frequency characteristic extraction module: obtain the open-loop gain and phase response curve of the target low-noise operational amplifier at different frequency points, and extract the low-frequency cutoff point ω1, the unity gain frequency ωu and the maximum phase lag θm.

[0024] The low-noise operational amplifier is tested in open-loop connection. By disconnecting the closed-loop feedback path, a sinusoidal excitation signal with constant amplitude is applied to the input, and the output response is measured using a vector network analyzer. The frequency scanning range is set to 10 Hz to 10 MHz, and the open-loop gain (in decibels) and phase response (in degrees) data at each frequency point are recorded at linear intervals to obtain the complete frequency response curve.

[0025] The feature point extraction process is performed on the obtained frequency response curve. With open-loop gain as the vertical axis and frequency as the horizontal axis, the gain variation trend with frequency is analyzed, and the position where the open-loop gain first decreases and approaches 0 decibels is identified, i.e. the intersection point of the gain curve and the 0 decibel line, defined as the unity gain frequency, denoted as ωu. If the intersection point falls between two sampling points, the linear interpolation method is used to calculate the accurate frequency value of the intersection point to improve the measurement accuracy.

[0026] The phase response data is fitted using a third-order polynomial curve fitting method. The phase response data is fitted with frequency f as the independent variable, and the fitting function is where a, b, c, d are the fitting coefficients, and the optimal solution is determined by the least squares method. At the point corresponding to the unity gain frequency ωu, the phase response angle at this frequency point is calculated by substituting the fitting function φ(f), and then the minimum phase angle value near this position is identified, and the minimum phase angle is defined as the maximum phase lag angle, denoted as θm. This parameter is used to reflect the stability margin of the operational amplifier near the unity gain point.

[0027] Based on the gain-frequency response slope variation law, the derivative method is used to detect the inflection point position of the frequency response curve to extract the low-frequency cutoff point frequency. First, the first derivative of the gain curve is calculated to construct the function G'(f), which represents the gain reduction rate under unit frequency change. In the low frequency region, the maximum value position of G'(f) is detected, which is the point where the gain decreases most rapidly, and the corresponding frequency is defined as the low-frequency cutoff point, denoted as ω1.

[0028] Compensation parameter construction module: construct the frequency compensation parameter group P={P1, P2,..., Pn}, where Pi={Ci, Ri}, Ci is the compensation capacitance value, Ri is the equivalent compensation resistance value, and Pn is the maximum compensation capacitive resistance range.

[0029] Based on the obtained unit gain frequency, maximum phase lag angle and low frequency cutoff point frequency, the value range of the compensation capacitor value is determined. The lower limit of the compensation capacitor value is calculated according to the target minimum phase margin. The upper limit is determined according to the stability constraint of the closed-loop system under direct current condition. When the compensation capacitor value exceeds the upper limit, it may cause a large decrease in direct current gain or uncontrolled pole migration, thereby causing zero drift or closed-loop oscillation.

[0030] Within the above-mentioned compensation capacitor value range, a plurality of compensation capacitor candidate values are generated according to a fixed linear step. Specifically, the step length is set as ΔC, the starting value is C1, and the maximum value is Cn. Then the compensation capacitor sequence is , i = 1 to n. For each compensation capacitor value, the corresponding equivalent compensation resistance value is calculated through the equivalent small signal model. The model is based on a second-order frequency response equation, and the resistance-capacitance relationship that can achieve the target zero-pole configuration is analytically solved under the condition that the preset gain-bandwidth product remains unchanged. The equivalent compensation resistance value can be calculated by the formula , where fi represents the target frequency position corresponding to the compensation pole, which is configured according to the actual application scenario.

[0031] Each compensation capacitor value is paired and combined with the corresponding calculated equivalent compensation resistance value to form a complete compensation parameter unit, denoted as , where Ci is the i-th compensation capacitor value, and Ri is the equivalent compensation resistance value matched therewith. All generated parameter units constitute a frequency compensation parameter set P = {P1, P2,..., Pn}, where Pn is the maximum numbered parameter unit.

[0032] Finally, all parameter units are sorted according to the impedance amplitude value formed by the compensation capacitor value and the equivalent compensation resistance value in each parameter unit. The impedance amplitude value is defined as , where is the reference frequency. The compensation parameter unit with the largest impedance amplitude value is extracted through sorting, and is defined as the parameter corresponding to the maximum compensation impedance range, denoted as Pn. This parameter unit provides the strongest compensation capability under the condition of ensuring system stability, and is used to determine the boundary characteristics of the frequency compensation parameter group.

[0033] Frequency domain stability modeling module: based on the obtained ω1, ωu and θm characteristics, an initial frequency domain stability model M0 is constructed.

[0034] The target phase response curve in the frequency range and the open-loop gain envelope are defined with the unit gain frequency, the maximum phase lag angle, and the low-frequency cutoff point as the input boundary conditions. The above three parameters define the start and end positions of the working bandwidth of the model, the lower limit of stability, and the reference point of the zero-pole layout. On this basis, an ideal phase response curve is constructed as a target function for subsequent transfer function fitting.

[0035] An open-loop transfer function model is established. The transfer function form is defined as where G(s) represents the open-loop response function of the low-noise operational amplifier in the Laplace domain, A is the low-frequency gain constant, ω1 is the low-frequency pole frequency corresponding to the low-frequency cutoff point, and ωz is the compensation zero frequency used to improve the phase margin near the unit gain frequency. s is the independent variable in the complex frequency domain (complex Laplace domain), which is used to represent the frequency response or dynamic behavior of a system. The transfer function is a standard second-order single-input single-output system function with one low-frequency pole and one mid-frequency zero. By adjusting the three variables A, ω1, and ωz, the measured gain-phase response data under the aforementioned boundary conditions are fitted, so that the model response curve approximates the measured curve.

[0036] The open-loop transfer function model and each compensation parameter unit in the compensation parameter group are coupled to form a frequency response mapping model. The compensation parameter unit is Pi={Ci, Ri} formed in the aforementioned construction process, where Ci is the compensation capacitance value and Ri is the corresponding equivalent compensation resistance value. According to the definition relationship of ωz in the transfer function, ωz is expressed as and substituted into the expression of G(s) to realize the quantitative coupling of the compensation parameter and the model frequency characteristic. In this way, each compensation parameter unit Pi corresponds to a unique Gi(s) expression, and its frequency response function is obtained.

[0037] The initial frequency domain stability model is defined as the response function set containing the above frequency response mapping relationship, denoted as M0={G1(s), G2(s),..., Gn(s)}, where n is the number of compensation parameter units. Each Gi(s) expression can be analyzed in the same frequency scanning range, which is convenient for subsequent extraction of stability indicators such as phase margin and gain margin through numerical methods.

[0038] Frequency scanning simulation module: the frequency compensation parameter group P is sequentially imported into the initial frequency domain stability model M0, and the stability function F(Pi) under each compensation configuration is obtained through frequency scanning simulation, and each group Pi is marked to see if it meets the stability critical condition F(Pi)≥Φ0, where Φ0 is the preset minimum phase margin.

[0039] Each compensation parameter unit generated in the frequency compensation parameter group is sequentially substituted into the initial frequency domain stability model to generate its corresponding frequency response function. Specifically, for any set of compensation parameter units Pi={Ci, Ri}, where Ci is the compensation capacitance value and Ri is the equivalent compensation resistance value, according to the coupling relationship established in the foregoing frequency domain modeling step, substitute into the open-loop transfer function expression G(s) to form a complete frequency response function Gi(s). The function can describe the gain and phase response characteristics of the system in the frequency domain under compensation conditions.

[0040] Numerical simulation is performed on the frequency response function within the set frequency scanning range. The frequency scanning range is set to 10 Hz to 10 MHz, and is discretely scanned in a logarithmic coordinate uniform sampling manner. For each response function Gi(s), the phase response curve is solved at the scanning frequency points, and the phase angle value corresponding to the unit gain frequency is extracted. The unit gain frequency is the frequency point at which the gain of the frequency response function first drops to 0 decibels.

[0041] The extracted phase response value is compared with the preset minimum phase margin threshold to construct a stability function expression. Let be the phase response value of the compensation parameter unit Pi at the unit gain frequency, and Φ0 be the stability judgment threshold (usually set to 45 degrees), then the stability function is defined as: where is the phase response corresponding to the compensation parameter unit; when F(Pi) is greater than or equal to 0, it indicates that the phase margin under the compensation configuration meets the minimum stability requirement.

[0042] Numerical judgment is performed on the stability function values corresponding to each compensation parameter unit. If the stability function value of a certain unit is greater than or equal to zero, i.e., it meets the stability margin condition, then the compensation parameter unit is assigned a "qualified" label; if it is less than zero, it is assigned an "unqualified" label, which is used to eliminate parameter combinations that do not have engineering feasibility in the subsequent optimization process.

[0043] All compensation parameter units that have completed judgment and are labeled with labels are unified and arranged into a structured result set. The structured result set includes the compensation capacitance value, compensation resistance value, stability function value, and corresponding effectiveness label of each compensation parameter unit. The result set is recorded in a two-dimensional structure and can be represented in the form of a table or data matrix, facilitating subsequent sorting and screening operations.

[0044] To facilitate the selection of the optimal compensation strategy, the compensation parameter units marked as "qualified" are sorted according to the size of their stability function values. The sorting can be in ascending order or descending order, and the selection is based on the system design goals. For example, if the maximum phase margin is prioritized, the compensation parameter units can be arranged in descending order of F(Pi), and the compensation parameter unit corresponding to the maximum value is extracted for final feedback to the amplifier circuit design link.

[0045] Optimal compensation extraction module: According to the F(Pi) marking result, the minimum compensation parameter set P* that meets the stability requirement is extracted, and P* is fed back to adjust the original amplifier frequency compensation link.

[0046] From the compensation parameter units marked as "qualified" in the aforementioned frequency scanning simulation and stability function judgment steps, the parameter set with all stability function values greater than zero is screened out. Let the stability function be where represents the phase response angle at the unity gain frequency, and Φ0 is the minimum phase margin threshold (such as 45 degrees). Only when F(Pi)>0, it means that the corresponding compensation parameter unit not only meets the minimum phase margin requirement, but also has a certain margin space and has the potential for further optimization. All parameter units that meet this condition are recorded as the candidate compensation set S1.

[0047] Based on the preset optimization goal, the total equivalent capacitance of each compensation parameter unit is defined as an evaluation index, which is used to measure the occupation degree of the compensation loop to the system resources. The capacitance amplitude Through the equivalent formula of resistance-capacitance series, it is defined as: ; where is the equivalent compensation resistance value, is the compensation capacitance value, is the unity gain frequency, and the capacitance unit is ohm. This index comprehensively considers the impedance characteristics under the joint influence of capacitance and resistance, and is used to compress the compensation resources while maintaining stability.

[0048] Under the premise of ensuring that the stability function value is positive, the parameter unit with the smallest capacitance amplitude is extracted from the candidate compensation set S1, and is recorded as P*. P* is the set of parameters that meet the phase margin requirement, with the smallest circuit resource consumption and the highest frequency response efficiency, and has realizability and optimality.

[0049] The obtained minimum compensation parameter set P* is fed back to the frequency compensation loop of the original low-noise operational amplifier, and the specific device parameter replacement or circuit structure adjustment is performed according to the compensation capacitance value C* and the equivalent compensation resistance value R*. The specific mode includes replacing the compensation capacitance component in the feedback network, adjusting the transconductance stage resistance matching unit, or updating the operational amplifier internal frequency compensation pole design according to the zero point position calculated by P*, so as to ensure that the frequency stability performance consistent with the simulation expectation is realized in the actual application.

[0050] Through the above minimum compensation parameter extraction and feedback process, the minimum configuration of the frequency compensation resource can be realized while meeting the circuit stability requirement, and the synergy of the analog front end in power consumption, area, phase margin and other performance indicators is effectively improved.

[0051] The low-noise operational amplifier frequency compensation method provided by the application constructs an initial frequency domain stability model around the unit gain frequency, the maximum phase lag angle and the low-frequency cutoff point and other frequency domain characteristic parameters, and performs frequency scanning simulation combined with the compensation parameter group, realizes the quantitative evaluation of the phase margin and the function mapping of the compensation effect, accurately selects the compensation parameter unit meeting the stability requirement through the stability function judgment and the label marking mechanism, and further extracts the capacitor-resistor combination with the minimum resource occupation under the condition of ensuring the phase margin by using the minimum capacitance resistance optimization strategy, and feeds back to the frequency compensation loop design, which significantly improves the compensation efficiency and system stability.

[0052] The above is only a specific embodiment of the application, but the protection scope of the application is not limited thereto, and any person skilled in the art can easily think of changes or replacements within the technical range disclosed by the application, which should be covered within the protection scope of the application.

Claims

1. A low noise operational amplifier frequency compensation system based on, characterized by: include: Frequency response extraction module: Obtain the open-loop gain and phase response curves of the target low-noise operational amplifier at different frequency points, and extract its low-frequency cutoff point ω1, unity-gain frequency ωu, and maximum phase hysteresis θm; Compensation parameter construction module: Constructs a frequency compensation parameter group P={P1,P2,...,Pn}, where Pi={Ci,Ri}, Ci is the compensation capacitor value, Ri is the equivalent compensation resistance value, and Pn is the maximum compensation capacitive reactance range; The frequency domain stability modeling module comprises the following steps: constructing an initial frequency domain stability model M0 based on the obtained ω1, ωu and θm characteristics, specifically comprising: taking the unity gain frequency, the maximum phase lag angle and the low frequency cutoff point as the input boundary conditions, defining the target phase response curve and the open loop gain envelope line in the frequency range; establishing an open loop transfer function model wherein ω1 is a low frequency pole frequency, ωz is a compensation zero frequency, A is a low frequency gain constant, and s is an independent variable in a complex frequency domain; coupling the open loop transfer function model with each compensation parameter unit in the compensation parameter group to form a frequency response mapping model; defining the initial frequency domain stability model M0 as a response function set containing the frequency response mapping relationship; Frequency scanning simulation module: The frequency compensation parameter group P is sequentially imported into the initial frequency domain stability model M0. The stability function F(Pi) under each compensation configuration is obtained through frequency scanning simulation. Each group of Pi is marked as to whether the stability critical condition F(Pi)≥Φ0 is satisfied, where Φ0 is the preset minimum phase margin. The optimal compensation extraction module extracts the minimum compensation parameter set P* that meets the stability requirements based on the F(Pi) marking results. P* is then used to adjust the original amplifier's frequency compensation circuit. Specifically, this includes: selecting all parameters with stability function values ​​greater than zero from the compensation parameter units that have been assigned qualified labels; calculating the total equivalent capacitive reactance of each parameter unit based on the pre-set optimization objective, using the capacitive reactance amplitude formed by the compensation capacitor value and the equivalent compensation resistor value as an evaluation index; extracting the parameter unit with the smallest capacitive reactance amplitude from the selection results, under the condition that the stability function value is non-negative, to form the minimum compensation parameter set; and feeding back the minimum compensation parameter set to adjust the original amplifier's frequency compensation circuit structure.

2. The frequency compensation system based on low-noise operational amplifier according to claim 1, characterized in that: The frequency characteristic extraction module includes: Open-loop connection tests were performed on the low-noise operational amplifier to obtain open-loop gain and phase response data curves within a preset frequency scanning range; Feature point extraction processing was performed on the acquired frequency response curve to identify the unity gain frequency ωu corresponding to the first drop in open-loop gain to 0dB. The phase response data were fitted using a third-order curve fitting method to calculate the phase angle at the unity-gain frequency and determine its maximum phase lag θm. Based on the gain-frequency response slope variation law, the inflection point position is detected by the derivative method, thereby extracting the corresponding low-frequency cutoff point ω1.

3. The frequency compensation system based on low noise operational amplifier according to claim 2, characterized in that: The compensation parameter construction module includes: Based on the pre-measured unity-gain frequency, maximum phase lag angle, and low-frequency cutoff frequency of the low-noise operational amplifier, the range of values ​​for the compensation capacitor is determined. The lower limit is limited by the minimum phase margin requirement, and the upper limit is limited by the DC stability condition. Multiple compensation capacitor values ​​are generated within the range of compensation capacitor values ​​according to a preset incremental step size. Based on the equivalent small signal model, the equivalent compensation resistance value corresponding to each compensation capacitor value is analytically calculated so that the two form a one-to-one parameter pair. Each compensation capacitor value is combined with its corresponding equivalent compensation resistor value to form a compensation parameter unit Pi={Ci,Ri}, where Ci is the compensation capacitor value, Ri is the equivalent compensation resistor value, and Pn is the maximum compensation capacitive reactance range. All compensation parameter units are sorted according to the capacitive reactance amplitude formed by the compensation capacitor value and the equivalent compensation resistor value, and the compensation parameter unit with the largest capacitive reactance amplitude is defined as the maximum compensation capacitive reactance range, so as to construct a complete frequency compensation parameter group P.

4. The frequency compensation system based on low noise operational amplifier according to claim 1, characterized in that: The frequency scanning simulation module includes: Substitute each compensation parameter unit in the frequency compensation parameter group into the initial frequency domain stability model in sequence to generate the corresponding frequency response function; Within the set frequency scanning range, numerical simulations are performed on each frequency response function to extract the phase response value at the unity gain frequency. The extracted phase response value is compared with a preset minimum phase margin threshold to construct a stability function. ,in The phase response under the corresponding compensation parameter unit; Determine whether each stability function value is greater than or equal to zero, and label each set of compensation parameter units according to the determination result to distinguish those that meet the stability requirements and those that do not.

5. A frequency compensation system based on a low-noise operational amplifier according to claim 4, characterized in that: Determine whether each stability function value is greater than or equal to zero, and label each set of compensation parameter units according to the determination result, including: The stability function values ​​corresponding to each compensation parameter unit in the frequency scanning simulation results are numerically judged. If the function value is greater than or equal to zero, the stability requirement is considered to be met. Compensation parameter units that meet the judgment conditions are assigned a qualified mark, and compensation parameter units that do not meet the judgment conditions are assigned a unqualified mark. All labeled compensation parameter units are organized into a structured label result set, which includes compensation capacitor value, compensation resistor value, stability function value and corresponding label; The qualified identification units are sorted in ascending or descending order according to the magnitude of the stability function value.

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