Switched capacitor notch filter for chopping stabilized amplifier

Abstract

The invention provides a switched capacitor notch filter for a chopping stabilized amplifier. The switched capacitor notch filter comprises a first-stage chopper, a second-stage chopper, an amplifier GM1, a first-stage amplifier GM1F, a second-stage amplifier GM2, a third-stage amplifier GM3 and the switched capacitor notch filter. The filter comprises differential capacitors C1-C2 and single-ended capacitors C3-C6, the single-ended capacitors realize control of DC voltage of an input end on an output end, and voltage drift is avoided; the clock frequency is 1 / 2 of that of a chopper clock, the transmission voltage is sampled only at the edge center of the output waveform of the chopper, and the ripple is reduced. The DC bias establishment speed can be increased, only one path of architecture is needed, the power consumption and the chip area are greatly reduced, and the method is suitable for a high-precision measurement scene.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of analog chip design, and in particular to a switched-capacitor notch filter for a chopping stabilized amplifier. BACKGROUND

[0002] In high-precision measurement scenarios, the operational amplifier needs to have both low offset voltage and low temperature drift characteristics to ensure the accuracy of the measurement results. Chopping stabilized amplifiers effectively suppress offset voltage and temperature drift through chopping technology, becoming the mainstream selection in this field. However, the introduction of chopping technology will cause a large swing ripple disturbance at the output end of the amplifier (caused by the chopping switch frequency and its frequency multiplication noise), which severely restricts the improvement of high-precision measurement performance.

[0003] To solve the above ripple problem, switched-capacitor (SC) notch filters are widely used in ripple filtering circuits of chopping stabilized amplifiers because they have comb-shaped frequency domain characteristics and can form deep suppression at the chopping switch frequency and its frequency multiplication. 1. Technical solution based on CN115395923A CN115395923A discloses a chopping stabilized amplifier that reduces output stage ripple swing by introducing an SC notch filter. The structure of the notch filter is as shown in Figure 1 The corresponding control timing is as shown in Figure 2 The chopping switch timing phase1, phase2 and the notch filter switch timing phase3, phase4 are generated by internal clock division, where phase3 lags phase1 by 90°, and phase4 lags phase2 by 90°. The notch filter transfers the front-stage mismatch integration voltage to the back-stage at the falling edge of phase3 and phase4.

[0004] In theory, the rising edge and the falling edge of phase3 and phase4 are mirror images, and the transferred voltage values are consistent. However, in practical applications, there are two major problems: first, the rising edge and the falling edge of the chopping output are not completely symmetrical; second, the phase lag of phase3 and phase1, and phase4 and phase2 is difficult to control accurately at 90°, resulting in residual ripple of tens of microvolts to hundreds of microvolts at the output end of the amplifier, which is difficult to adapt to higher-precision application scenarios (such as Figure 3

[0005] ​Further, the SC notch filter in this scheme adopts a differential capacitor structure composed of C5 and C6, which can quickly transmit the differential signal quantity, but the transmission speed of the direct current (DC) direct current quantity is extremely slow, resulting in slow establishment of the direct current bias voltage of the output nodes 22A and 22B of the notch filter, and voltage drift is prone to occur. To alleviate this problem, CN115395923A adds a pre-charge circuit (as shown in Figure 4 The pre-charge circuit provides a fast establishment path for the output end of the notch filter and locks the voltage to VB, thereby improving the bias voltage establishment speed. However, when the voltage of the nodes 22A and 22B is higher than VB due to factors such as the leakage of the Mp2 and Mp3 tubes and drift occurs, the correction speed of the pre-charge circuit is still insufficient. The core reason is the lack of a stable and fast direct current bias point constraint mechanism.

[0006] 2. Technical scheme based on CN110932673A CN110932673A discloses another chopper stabilized amplifier structure (as shown in Figure 5 It adopts two sets of SC notch filters, which are respectively output to the input ends of the amplifiers GM2 and GM4, and the output ends of GM2 and GM4 are connected to the input end of GM3 after being short-circuited with the output end of GMFF. The timing design of this scheme is as shown in Figure 6 The working frequency of the SC notch filter is half of the chopping frequency, and the falling edges of the control timing of the two sets of filters correspond to the middle points of the high level and the low level of PHASE1, respectively. A single notch filter only samples the middle point of the rising edge or the falling edge of the output signal of the chopper, thereby avoiding the ripples generated at the input ends of GM2 and GM4 due to factors such as the asymmetry of the rising edge and the falling edge and timing delay, and achieving a significant reduction in the ripple swing.

[0007] However, this scheme has a significant defect: two sets of notch filters, subsequent amplification units, and Miller feedback capacitors need to be additionally configured, resulting in a significant increase in circuit power consumption and chip area, which is not conducive to cost control and low-power system design. At the same time, similar to CN115395923A, the notch filter in this scheme only contains a differential capacitor, and the same problem of slow establishment and easy drift of the direct current bias voltage at the output end exists.

[0008] In summary, the existing chopper stabilized amplifier ripple suppression schemes have defects such as residual ripple and unstable direct current bias, or have problems such as excessive power consumption and area, and it is difficult to meet the application requirements of high precision, low power consumption, and miniaturization at the same time. SUMMARY

[0009] The application provides a novel switched-capacitor notch filter applied to a chopper stabilized amplifier, wherein, in addition to differential capacitors, single-end capacitors are introduced into the filter, so that the control of the input end direct current voltage of the switched-capitor filter on the output end is realized, the establishment speed of the output end of the switched-capitor filter is accelerated, and the output waveform distortion caused by the voltage drift of the output end of the switched-capitor filter is avoided.

[0010] The application provides a switched-capacitor notch filter for a chopper stabilized amplifier, wherein the chopper stabilized amplifier comprises a first-stage chopper, a second-stage chopper, an amplifier GM1, a first-stage amplifier GM1F, a second-stage amplifier GM2, a third-stage amplifier GM3 and the switched-capacitor notch filter. The first-stage chopper is connected to the input end of the amplifier GM1 and the input end of the first-stage amplifier GM1F. The second-stage chopper is connected to the output end of the amplifier GM1 and the input end of the switched-capacitor notch filter. The second-stage amplifier GM2 is connected to the output end of the switched-capacitor notch filter and the input end of the third-stage amplifier GM3. The output end of the third-stage amplifier GM3 is connected to the output end of the chopper stabilized amplifier. The input end of the chopper stabilized amplifier is connected to the input end of the first-stage amplifier GM1F, and the output end of the first-stage amplifier GM1F is connected to the input end of the third-stage amplifier GM3.

[0011] In an embodiment of the application, the switched-capacitor notch filter comprises a first switch, a second switch, a third switch, a fourth switch, a fifth switch, a sixth switch, a seventh switch, an eighth switch, a first capacitor C1, a second capacitor C2, a third capacitor C3, a fourth capacitor C4, a fifth capacitor C5, a sixth capacitor C6 and a seventh capacitor C7. The first end of the first switch is connected to the positive input end, and the second end of the first switch is connected to the first end of the second switch. The second end of the second switch is connected to the positive output end, the first end of the second switch is connected to the first end of the third capacitor C3, and the second end of the third capacitor C3 is grounded. The first end of the fifth switch is connected to the positive input end, and the second end of the fifth switch is connected to the first end of the sixth switch; The second end of the sixth switch is connected to the positive output end, the first end of the sixth switch is connected to the first end of the fifth capacitor C5, and the second end of the fifth capacitor C5 is grounded. The first end of the third switch is connected to the negative input end, and the second end of the third switch is connected to the first end of the fourth switch. The second end of the fourth switch is connected to the negative output end, the first end of the fourth switch is connected to the first end of the fourth capacitor C4, and the second end of the fourth capacitor C4 is grounded. The first end of the seventh switch is connected to the negative input end, and the second end of the seventh switch is connected to the first end of the eighth switch. The second end of the eighth switch is connected to the negative output end, the first end of the eighth switch is connected to the first end of the sixth capacitor C6, and the second end of the sixth capacitor C6 is grounded. The first end of the first capacitor C1 is connected to the second end of the second switch, and the second end of the first capacitor C1 is connected to the first end of the fourth switch. The first end of the second capacitor C2 is connected to the first end of the sixth switch, and the second end of the second capacitor C2 is connected to the second end of the eighth switch. The first end of the seventh capacitor C7 is connected to the positive output end, and the second end of the seventh capacitor C7 is connected to the negative output end.

[0012] In an embodiment of the present application, the switched capacitor notch filter comprises: a first switch, a second switch, a third switch, a fourth switch, a fifth switch, a sixth switch, a seventh switch, an eighth switch, a third capacitor C3, a fourth capacitor C4, a fifth capacitor C5, a sixth capacitor C6, and a seventh capacitor C7. The first end of the first switch is connected to the positive input end, and the second end of the first switch is connected to the first end of the second switch. The second end of the second switch is connected to the positive output end, the first end of the second switch is connected to the first end of the third capacitor C3, and the second end of the third capacitor C3 is grounded. The first end of the fifth switch is connected to the positive input end, and the second end of the fifth switch is connected to the first end of the sixth switch. The second end of the sixth switch is connected to the positive output end, the first end of the sixth switch is connected to the first end of the fifth capacitor C5, and the second end of the fifth capacitor C5 is grounded. The first end of the third switch is connected to the negative input end, and the second end of the third switch is connected to the first end of the fourth switch. The second end of the fourth switch is connected to the negative output end, the first end of the fourth switch is connected to the first end of the fourth capacitor C4, and the second end of the fourth capacitor C4 is grounded. The first end of the seventh switch is connected to the negative input end, and the second end of the seventh switch is connected to the first end of the eighth switch. The eighth switch second end is connected to the negative output end, and the eighth switch first end is connected to the sixth capacitor C6 first end, and the sixth capacitor C6 second end is grounded. The seventh capacitor C7 first end is connected to the positive output end, and the seventh capacitor C7 second end is connected to the negative output end.

[0013] In an embodiment of the present application, further comprising: The capacitor CFB1 first end is connected to the switch capacitor wave filter positive input end, and the capacitor CFB1 second end is connected to the third stage amplifier GM3 output end. The capacitor CFB2 first end is connected to the second stage amplifier GM2 positive input end, and the capacitor CFB2 second end is connected to the third stage amplifier GM3 output end. The capacitor C8 first end is connected to the third stage amplifier GM3 input end, and the capacitor C8 second end is connected to the third stage amplifier GM3 output end. The capacitor C9 first end is connected to the switch capacitor wave filter negative input end, and the capacitor C9 second end is grounded. The capacitor C10 first end is connected to the switch capacitor wave filter negative output end, and the capacitor C10 second end is grounded.

[0014] In an embodiment of the present application, the chopper stabilized amplifier controls the chopping output signal through the first clock signal and the second clock signal, and the phase interval of the first clock signal and the second clock signal is 180 degrees.

[0015] In an embodiment of the present application, the first switch, the third switch, the sixth switch and the eighth switch are controlled through the third clock signal. The second switch, the fourth switch, the fifth switch and the seventh switch are controlled through the fourth clock signal.

[0016] In an embodiment of the present application, the phase interval of the third clock signal and the fourth clock signal is 180 degrees.

[0017] In an embodiment of the present application, the clock frequency of the third clock signal and the fourth clock signal is one half of the first clock signal.

[0018] In an embodiment of the present application, the switch capacitor wave filter only carries out voltage collection and transmission at one half of the positive level of the first clock signal.

[0019] The present application has the following beneficial effects: (1) Introducing single-ended capacitors C3-C6, realizing direct control of the input DC voltage on the output, accelerating the establishment speed of the output DC bias voltage. Effectively constrain the output voltage drift, avoid the output waveform distortion caused by drift, adapt to high-precision application requirements.

[0020] (2) The filter clock frequency is half of the chopper clock frequency, and only the rising or falling edge of the chopper output waveform is sampled and transmitted. It is not sensitive to the asymmetry of the rising and falling edges and the delay between clock signals, further reducing the output ripple amplitude, which is superior to existing solutions.

[0021] (3) Only one switched capacitor notch filter and a subsequent amplifier are required, which greatly reduces power consumption and chip area compared to the two sets of architecture of CN110932673A. By increasing the chopping frequency and increasing the feedback capacitor ratio, the delay instability problem caused by single-channel architecture can be avoided, and performance and cost are considered. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 The notch filter structure diagram in the prior art CN115395923A is shown; Figure 2 The chopping switch and notch filter switch timing diagram in the prior art CN115395923A is shown; Figure 3 The clock and ripple generation timing diagram in the prior art CN115395923A is shown; Figure 4 The pre-charge circuit diagram in the prior art CN115395923A is shown; Figure 5 The chopping stable amplifier structure diagram in the prior art CN110932673A is shown; Figure 6 The chopping and switched capacitor filter timing diagram in the prior art CN110932673A is shown; Figure 7 The switched capacitor notch filter structure diagram for the chopping stable amplifier in an embodiment of the present application is shown; Figure 8 The switched capacitor notch filter circuit diagram in an embodiment of the present application is shown; Figure 9 The output comparison diagram in an embodiment of the present application is shown; Figure 10 The chopping and switched capacitor notch filter timing diagram in an embodiment of the present application is shown; and Figure 11 The switched capacitor notch filter circuit diagram in another embodiment of the present application is shown. DETAILED DESCRIPTION

[0023] In the following description, the invention is described with reference to various embodiments. However, those skilled in the art will recognize that the embodiments may be practiced without one or more specific details or with other alternatives and / or additional methods, materials, or components. In other instances, well-known structures, materials, or operations are not shown or described in detail so as not to obscure the inventive points of the invention. Similarly, for illustrative purposes, specific quantities, materials, and configurations are set forth to provide a comprehensive understanding of embodiments of the invention. However, the invention is not limited to these specific details.

[0024] In this invention, the various embodiments are merely intended to illustrate the solutions of the invention and should not be construed as limiting.

[0025] In this specification, references to "an embodiment" or "this embodiment" mean that a particular feature, structure, or characteristic described in connection with that embodiment is included in at least one embodiment of the invention. The phrase "in one embodiment" appearing throughout this specification does not necessarily refer to the same embodiment in all instances.

[0026] Furthermore, the numbering of the steps in the methods of the present invention does not limit the execution order of the method steps. Unless otherwise specified, the method steps may be executed in different orders.

[0027] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0028] Figure 7 A schematic diagram of a switched-capacitor notch filter for chopper-stabilized amplifiers is shown in one embodiment of the present invention.

[0029] like Figure 7 As shown, in one embodiment of the present invention, the switched-capacitor notch filter for chopper-stabilized amplifier includes: First-stage chopper 110, second-stage chopper 120, amplifier GM1 200, first-stage amplifier GM1F 210, second-stage amplifier GM2 220, third-stage amplifier GM3 230, switched-capacitor notch filter 300, capacitor CFB1 410, capacitor CFB2 420, capacitor C8 430, capacitor C9 440, capacitor C10 450.

[0030] The first-stage chopper 110 is connected to the input terminal of amplifier GM1 200 and the input terminal of first-stage amplifier GM1F 210; The second-stage chopper 120 is connected to the output of amplifier GM1 200 and the input of switched-capacitor notch filter 300; The second-stage amplifier GM2 220 is connected to the output of the switched-capacitor notch filter 300 and the input of the third-stage amplifier GM3230. The output of the third-stage amplifier GM3 230 is connected to the output of the chopper-stabilized amplifier; The input terminal of the chopper stabilizer amplifier is connected to the input terminal of the first-stage amplifier GM1F210, and the output terminal of the first-stage amplifier GM1F210 is connected to the input terminal of the third-stage amplifier GM3230. The first terminal of capacitor CFB1 410 is connected to the positive input terminal of switched capacitor notch filter 300, and the second terminal of capacitor CFB1 410 is connected to the output terminal of third stage amplifier GM3 230; The first terminal of capacitor CFB2 420 is connected to the positive input terminal of the second-stage amplifier GM2 220, and the second terminal of capacitor CFB2 420 is connected to the output terminal of the third-stage amplifier GM3 230. The first terminal of capacitor C8 430 is connected to the input terminal of the third-stage amplifier GM3 230, and the second terminal of capacitor C8 430 is connected to the output terminal of the third-stage amplifier GM3 230. The first terminal of capacitor C9 440 is connected to the negative input terminal of the switched capacitor notch filter 300, and the second terminal of capacitor C9 440 is grounded. The first terminal of capacitor C10 450 is connected to the negative output terminal of the switched capacitor notch filter 300, and the second terminal of capacitor C10 450 is grounded.

[0031] Figure 8 A circuit diagram of a switched-capacitor notch filter according to an embodiment of the present invention is shown. like Figure 8 As shown, in this embodiment, the switched capacitor notch filter includes: First switch 310, second switch 311, third switch 312, fourth switch 313, fifth switch 314, sixth switch 315, seventh switch 316, eighth switch 317, first capacitor C1 321, second capacitor C2 322, third capacitor C3 323, fourth capacitor C4 324, fifth capacitor C5 325, sixth capacitor C6 326, seventh capacitor C7 327; Wherein, the first terminal of the first switch 310 is connected to the positive input terminal, and the second terminal of the first switch 310 is connected to the first terminal of the second switch 311; The second terminal of the second switch 311 is connected to the positive output terminal, the first terminal of the second switch 311 is connected to the first terminal of the third capacitor C3323, and the second terminal of the third capacitor C3323 is grounded. The first terminal of the fifth switch 314 is connected to the positive input terminal, and the second terminal of the fifth switch 314 is connected to the first terminal of the sixth switch 315. The second end of the sixth switch 315 is connected to the positive output end, and the first end of the sixth switch 315 is connected to the first end of the fifth capacitor C5 325, and the second end of the fifth capacitor C5 325 is grounded. The first end of the third switch 312 is connected to the negative input end, and the second end of the third switch 312 is connected to the first end of the fourth switch 313. The second end of the fourth switch 313 is connected to the negative output end, and the first end of the fourth switch 313 is connected to the first end of the fourth capacitor C4 324, and the second end of the fourth capacitor C4 324 is grounded. The first end of the seventh switch 316 is connected to the negative input end, and the second end of the seventh switch 316 is connected to the first end of the eighth switch 317. The second end of the eighth switch 317 is connected to the negative output end, and the first end of the eighth switch 317 is connected to the first end of the sixth capacitor C6 326, and the second end of the sixth capacitor C6 326 is grounded. The first end of the first capacitor C1 321 is connected to the second end of the second switch 311, and the second end of the first capacitor C1 321 is connected to the first end of the fourth switch 313. The first end of the second capacitor C2 322 is connected to the first end of the sixth switch 315, and the second end of the second capacitor C2 322 is connected to the second end of the eighth switch 317. The first end of the seventh capacitor C7 327 is connected to the positive output end, and the second end of the seventh capacitor C7 327 is connected to the negative output end.

[0032] The capacitors C1-C6 integrate and sample IN+ and IN-. In order to reduce the integral signal swing caused by the input mismatch of GM1 at IN+ and IN-, it is necessary to increase the capacitance of the sampling capacitor, but this will increase the chip area and increase the chip cost. Taking the third clock signal PH3 as an example, at this time, the sampling capacitor value of IN+ and IN- is C1+1 / 2C3+1 / 2C4, and C3 and C4 are single-ended capacitors contributing to the differential input end and need to be divided by 2. Therefore, in order to achieve a certain sampling capacitor value, the most cost-effective way is to use only the differential capacitor C1, not the single-ended capacitors C3 and C4. However, using only the differential capacitor C1 can only transmit the differential quantity of IN+ and IN-, and cannot control the DC bias voltage of the output end. The pre-charge circuit proposed in CN115395923A can preset the DC bias voltage of the output point of the switched capacitor notch filter, but when the pre-charge circuit is turned off, there is no circuit to correct the drift of the output point of the notch filter. The invention introduces capacitors C3-C6 to realize the transmission of the DC bias voltage of IN+ and IN- to OUT+ and OUT-, respectively, avoiding the drift of the bias voltage of the output stage of the notch filter. The differential capacitors C1 and C2 are the main capacitors for integrating and sampling the front stage, and the main function of the capacitors C3-C6 is to transmit the DC operating point of the front stage to the output stage.

[0033] Figure 11 A circuit diagram of a switched capacitor notch filter according to another embodiment of the present invention is shown.

[0034] like Figure 11 As shown, in another embodiment of the present invention, the switched capacitor notch filter includes: First switch 310, second switch 311, third switch 312, fourth switch 313, fifth switch 314, sixth switch 315, seventh switch 316, eighth switch 317, third capacitor C3 323, fourth capacitor C4 324, fifth capacitor C5 325, sixth capacitor C6 326, seventh capacitor C7 327; Wherein, the first terminal of the first switch 310 is connected to the positive input terminal, and the second terminal of the first switch 310 is connected to the first terminal of the second switch 311; The second terminal of the second switch 311 is connected to the positive output terminal, the first terminal of the second switch 311 is connected to the first terminal of the third capacitor C3323, and the second terminal of the third capacitor C3323 is grounded. The first terminal of the fifth switch 314 is connected to the positive input terminal, and the second terminal of the fifth switch 314 is connected to the first terminal of the sixth switch 315. The second terminal of the sixth switch 315 is connected to the positive output terminal, the first terminal of the sixth switch 315 is connected to the first terminal of the fifth capacitor C5325, and the second terminal of the fifth capacitor C5325 is grounded. The first terminal of the third switch 312 is connected to the negative input terminal, and the second terminal of the third switch 312 is connected to the first terminal of the fourth switch 313. The second terminal of the fourth switch 313 is connected to the negative output terminal, the first terminal of the fourth switch 313 is connected to the first terminal of the fourth capacitor C4324, and the second terminal of the fourth capacitor C4324 is grounded. The first terminal of the seventh switch 316 is connected to the negative input terminal, and the second terminal of the seventh switch 316 is connected to the first terminal of the eighth switch 317. The second terminal of the eighth switch 317 is connected to the negative output terminal, the first terminal of the eighth switch 317 is connected to the first terminal of the sixth capacitor C6326, and the second terminal of the sixth capacitor C6326 is grounded. The first terminal of the seventh capacitor C7 327 is connected to the positive output terminal, and the second terminal of the seventh capacitor C7 327 is connected to the negative output terminal.

[0035] Figure 9 A comparison diagram of outputs from one embodiment of the present invention is shown.

[0036] like Figure 9As shown, the effects of different capacitance values ​​of C3 to C6 on the settling time of OUT+ / OUT- are compared. Within a certain range, the larger the capacitance values ​​of C3 to C6, the faster the settling time, and vice versa. Without a single-ended capacitor, considering the parasitic capacitance in the actual circuit, OUT+ / OUT- will still eventually set up, but the settling time will be longer.

[0037] Figure 10 The timing diagram of a chopper and switched capacitor notch filter according to an embodiment of the present invention is shown.

[0038] like Figure 10 As shown, in one embodiment of the present invention, the chopper-stabilized amplifier controls the chopper output signal via a first clock signal PH1 and a second clock signal PH2. The first, third, sixth, and eighth switches are controlled by a third clock signal PH3; the second, fourth, fifth, and seventh switches are controlled by a fourth clock signal PH4. PH1 and PH2 are 180 degrees apart in phase and are used to control the chopper's path switching. PH3 and PH4 are 180 degrees apart in phase and are used to control the switched-capacitor filter's path switching. The clock frequency of PH3 is half that of PH1, and the rising edge of PH3 is located at half the positive level of PH1. Since the switched capacitor notch filter only samples and transmits voltage at half the positive level of PH1, that is, only at the center of the rising or falling edge of the chopper output waveform, the circuit is not sensitive to the asymmetry of the rising and falling edges, nor is it sensitive to the delay of PH3 relative to PH1. Compared with the solution proposed by CN115395923A, it can further reduce the output ripple amplitude, which is more advantageous for high-precision application scenarios.

[0039] Although various embodiments of the invention have been described above, it should be understood that they are presented by way of example only and not as limitations. It will be apparent to those skilled in the art that various combinations, modifications, and alterations can be made without departing from the spirit and scope of the invention. Therefore, the breadth and scope of the invention disclosed herein should not be limited by the exemplary embodiments disclosed above, but should be defined solely by the appended claims and their equivalents.

Claims

1. A switched-capacitor notch filter for a chopper-stabilized amplifier, characterized by, The chopper stabilized amplifier comprises a first stage chopper, a second stage chopper, an amplifier GM1, a first stage amplifier GM1F, a second stage amplifier GM2, a third stage amplifier GM3 and a switched capacitor notch filter; The first stage chopper is connected to the input end of the amplifier GM1 and the input end of the first stage amplifier GM1F; The second stage chopper is connected to the output end of the amplifier GM1 and the input end of the switched capacitor notch filter; The second stage amplifier GM2 is connected to the output end of the switched capacitor notch filter and the input end of the third stage amplifier GM3; The output end of the third stage amplifier GM3 is connected to the output end of the chopper stabilized amplifier; The input end of the chopper stabilized amplifier is connected to the input end of the first stage amplifier GM1F, and the output end of the first stage amplifier GM1F is connected to the input end of the third stage amplifier GM3.

2. The switched-capacitor notch filter for a chopper-stabilized amplifier of claim 1, wherein, The switched capacitor notch filter comprises a first switch, a second switch, a third switch, a fourth switch, a fifth switch, a sixth switch, a seventh switch, an eighth switch, a first capacitor C1, a second capacitor C2, a third capacitor C3, a fourth capacitor C4, a fifth capacitor C5, a sixth capacitor C6 and a seventh capacitor C7; The first end of the first switch is connected to the positive input end, and the second end of the first switch is connected to the first end of the second switch; The second end of the second switch is connected to the positive output end, and the first end of the second switch is connected to the first end of the third capacitor C3, and the second end of the third capacitor C3 is grounded; The first end of the fifth switch is connected to the positive input end, and the second end of the fifth switch is connected to the first end of the sixth switch; The second end of the sixth switch is connected to the positive output end, and the first end of the sixth switch is connected to the first end of the fifth capacitor C5, and the second end of the fifth capacitor C5 is grounded; The first end of the third switch is connected to the negative input end, and the second end of the third switch is connected to the first end of the fourth switch; The second end of the fourth switch is connected to the negative output end, and the first end of the fourth switch is connected to the first end of the fourth capacitor C4, and the second end of the fourth capacitor C4 is grounded; The first end of the seventh switch is connected to the negative input end, and the second end of the seventh switch is connected to the first end of the eighth switch; The second end of the eighth switch is connected to the negative output end, and the first end of the eighth switch is connected to the first end of the sixth capacitor C6, and the second end of the sixth capacitor C6 is grounded; The first end of the first capacitor C1 is connected to the second end of the second switch, and the second end of the first capacitor C1 is connected to the first end of the fourth switch; The first end of the second capacitor C2 is connected to the first end of the sixth switch, and the second end of the second capacitor C2 is connected to the second end of the eighth switch; The first end of the seventh capacitor C7 is connected to the positive output end, and the second end of the seventh capacitor C7 is connected to the negative output end.

3. The switched-capacitor notch filter for a chopper-stabilized amplifier of claim 1, wherein, The switched capacitor notch filter comprises a first switch, a second switch, a third switch, a fourth switch, a fifth switch, a sixth switch, a seventh switch, an eighth switch, a third capacitor C3, a fourth capacitor C4, a fifth capacitor C5, a sixth capacitor C6 and a seventh capacitor C7; The first end of the first switch is connected to the positive input end, and the second end of the first switch is connected to the first end of the second switch; The second end of the second switch is connected to the positive output end, and the first end of the second switch is connected to the first end of the third capacitor C3, and the second end of the third capacitor C3 is grounded; The first end of the fifth switch is connected to the positive input end, and the second end of the fifth switch is connected to the first end of the sixth switch; The second end of the sixth switch is connected to the positive output end, and the first end of the sixth switch is connected to the first end of the fifth capacitor C5, and the second end of the fifth capacitor C5 is grounded; The first end of the third switch is connected to the negative input end, and the second end of the third switch is connected to the first end of the fourth switch; The second end of the fourth switch is connected to the negative output end, and the first end of the fourth switch is connected to the first end of the fourth capacitor C4, and the second end of the fourth capacitor C4 is grounded; The first end of the seventh switch is connected to the negative input end, and the second end of the seventh switch is connected to the first end of the eighth switch; The second end of the eighth switch is connected to the negative output end, and the first end of the eighth switch is connected to the first end of the sixth capacitor C6, and the second end of the sixth capacitor C6 is grounded; The first end of the seventh capacitor C7 is connected to the positive output end, and the second end of the seventh capacitor C7 is connected to the negative output end.

4. The switched-capacitor notch filter for a chopper-stabilized amplifier of claim 1, wherein, Further comprising: The first end of the capacitor CFB1 is connected to the positive input end of the switched capacitor notch filter, and the second end of the capacitor CFB1 is connected to the output end of the third stage amplifier GM3; The first end of the capacitor CFB2 is connected to the positive input end of the second stage amplifier GM2, and the second end of the capacitor CFB2 is connected to the output end of the third stage amplifier GM3; The first end of the capacitor C8 is connected to the input end of the third stage amplifier GM3, and the second end of the capacitor C8 is connected to the output end of the third stage amplifier GM3; The first end of the capacitor C9 is connected to the negative input end of the switched capacitor notch filter, and the second end of the capacitor C9 is grounded; The first end of the capacitor C10 is connected to the negative output end of the switched capacitor notch filter, and the second end of the capacitor C10 is grounded.

5. The switched-capacitor notch filter for a chopper-stabilized amplifier of claim 1, wherein, The chopping stabilizing amplifier controls the chopping output signal through the first clock signal and the second clock signal, and the phase interval of the first clock signal and the second clock signal is 180 degrees.

6. The switched-capacitor notch filter for a chopper-stabilized amplifier of claim 2, wherein, The first switch, the third switch, the sixth switch and the eighth switch are controlled by the third clock signal; The second switch, the fourth switch, the fifth switch and the seventh switch are controlled by the fourth clock signal.

7. The switched-capacitor notch filter for a chopper-stabilized amplifier of claim 6, wherein, The phase interval of the third clock signal and the fourth clock signal is 180 degrees.

8. The switched-capacitor notch filter for a chopper-stabilized amplifier of claim 6, wherein, The clock frequency of the third clock signal and the fourth clock signal is half of the first clock signal.

9. The switched-capacitor notch filter for a chopper-stabilized amplifier of claim 1, wherein, The switched capacitor notch filter only collects and transmits voltage at half of the positive level of the first clock signal.

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