Multipath Instrumentation Amplifier

Abstract

A multipath instrumentation amplifier includes a low-frequency amplification circuit and a high-frequency amplification circuit coupled between a voltage input terminal and a voltage output terminal. The high-frequency amplification circuit includes a first amplifier, a second amplifier, a first input resistor, a first input capacitor, a second input resistor, a second input capacitor, a first feedback capacitor, and a second feedback capacitor. The inverting and non-inverting output terminals of the first amplifier are respectively coupled to the non-inverting and inverting input terminals of the second amplifier. The non-inverting and inverting output terminals of the second amplifier are coupled to the voltage output terminal. The first feedback capacitor is coupled between the voltage output terminal and the inverting input terminal of the first amplifier. The second feedback capacitor is coupled between the voltage output terminal and the non-inverting input terminal of the first amplifier.

Description

[Technical Field]

[0001] This invention relates to an instrumentation amplifier, and more particularly to a multipath instrumentation amplifier. [Previous Technology]

[0002] An instrumentation amplifier (IA) is a high-precision, low-skew, high common-mode rejection ratio (CMRR) differential amplifier, mainly used in signal processing circuits that require high precision, such as sensor signal amplification, medical electronics, and industrial measurement and communication equipment.

[0003] Instrumentation amplifiers contain multiple operational amplifiers. Generally, when the input signal is zero, an undesirable offset voltage will still appear at the output of the operational amplifier. This voltage usually originates from process variations in the operational amplifier. To reduce the impact of the operational amplifier's offset voltage, instrumentation amplifiers employ chopper stabilization. Chopper stabilization is a method that uses high-frequency modulation to reduce the DC offset voltage and low-frequency noise of operational amplifiers (Op-Amps) or other analog circuits. These low-frequency noises and DC offset voltages, modulated to a higher frequency, are then filtered out using a low-pass filter (LPF), resulting in a cleaner final output signal. However, chopper stabilization also generates high-frequency ripple voltage at the amplifier's output, which reduces the amplifier's stability and accuracy.

[0004] Therefore, the present invention addresses the above-mentioned problems by proposing a multipath instrumentation amplifier to solve the problems arising from conventional methods. [Summary of the Invention]

[0005] The present invention provides a multipath instrumentation amplifier that reduces output ripple voltage to increase stability and accuracy.

[0006] In one embodiment of the present invention, a multipath instrumentation amplifier is provided, which has a voltage input terminal and a voltage output terminal. The multipath instrumentation amplifier includes a low-frequency amplification circuit and a high-frequency amplification circuit. The low-frequency amplification circuit and the high-frequency amplification circuit are coupled between the voltage input terminal and the voltage output terminal. The voltage input terminal is coupled to an input voltage. The low-frequency amplification circuit and the high-frequency amplification circuit are used to amplify the input voltage and transmit the amplified input voltage to the voltage output terminal. The high-frequency amplification circuit is used to reduce voltage ripple on the voltage output terminal. The high-frequency amplification circuit includes a first amplifier, a second amplifier, a first input resistor, a first input capacitor, a second input resistor, a second input capacitor, a first feedback capacitor, and a second feedback capacitor. The inverting output terminal and the non-inverting output terminal of the first amplifier are respectively coupled to the non-inverting input terminal and the inverting input terminal of the second amplifier. The non-inverting output terminal and the inverting output terminal of the second amplifier are coupled to the voltage output terminal. A first input resistor and a first input capacitor are connected in series between a first reference voltage and the voltage input terminal. The node between the first input resistor and the first input capacitor is coupled to the non-inverting input terminal of the first amplifier. A second input resistor and a second input capacitor are connected in series between the first reference voltage and the voltage input terminal. The node between the second input resistor and the second input capacitor is coupled to the inverting input terminal of the first amplifier. A first feedback capacitor is coupled between the voltage output terminal and the inverting input terminal of the first amplifier. A second feedback capacitor is coupled between the voltage output terminal and the non-inverting input terminal of the second amplifier.

[0007] In one embodiment of the present invention, the low-frequency amplifier circuit includes a third amplifier, a first chopper, a third input capacitor, a fourth input capacitor, a second chopper, a fourth amplifier, a fifth amplifier, a third chopper, a third feedback capacitor, a first feedback resistor, a fourth feedback capacitor, and a second feedback resistor. The input terminal of the first chopper is coupled to a voltage input terminal, and the output terminal of the first chopper is coupled to the non-inverting input terminal and the inverting input terminal of the third amplifier through the third input capacitor and the fourth input capacitor, respectively. The input terminal of the second chopper is coupled to the inverting output terminal and the non-inverting output terminal of the third amplifier, respectively. The non-inverting input terminal and the inverting input terminal of the fourth amplifier are coupled to the output terminal of the second chopper. The non-inverting input terminal and the inverting input terminal of the fifth amplifier are coupled to the inverting output terminal and the non-inverting output terminal of the fourth amplifier, respectively. The inverting output terminal and the non-inverting output terminal of the fifth amplifier are coupled to the non-inverting input terminal and the inverting input terminal of the second amplifier, respectively. The third filter has a first input terminal and a second input terminal, and its output terminal is coupled to a voltage output terminal. The third feedback capacitor and the first feedback resistor are connected in parallel and coupled between the first input terminal of the third filter and the inverting input terminal of the third amplifier. The fourth feedback capacitor and the second feedback resistor are connected in parallel and coupled between the second input terminal of the third filter and the non-inverting input terminal of the third amplifier.

[0008] In one embodiment of the present invention, the multipath instrumentation amplifier further includes a resistor-capacitor circuit that is coupled to the inverting input terminal, non-inverting input terminal, inverting output terminal and non-inverting output terminal of the fourth amplifier and the second amplifier, and is used to perform frequency compensation for the low-frequency amplifier circuit and the high-frequency amplifier circuit.

[0009] In one embodiment of the present invention, the resistor-capacitor circuit is a low-pass filter.

[0010] In one embodiment of the present invention, the resistor-capacitor circuit includes a first compensation capacitor, a second compensation capacitor, a third compensation capacitor, a first compensation resistor, a fourth compensation capacitor, a second compensation resistor, a fifth compensation capacitor, and a sixth compensation capacitor. The first compensation capacitor is coupled between the non-inverting output terminal of the second amplifier and the inverting input terminal of the fourth amplifier. The second compensation capacitor is coupled between the inverting output terminal of the second amplifier and the non-inverting input terminal of the fourth amplifier. The third compensation capacitor and the first compensation resistor are connected in series and coupled between the inverting output terminal and the non-inverting input terminal of the fourth amplifier. The fourth compensation capacitor and the second compensation resistor are connected in series and coupled between the non-inverting output terminal and the inverting input terminal of the fourth amplifier. The fifth compensation capacitor is coupled between the non-inverting input terminal and the inverting output terminal of the second amplifier. The sixth compensation capacitor is coupled between the inverting input terminal and the non-inverting output terminal of the second amplifier.

[0011] In one embodiment of the present invention, the multipath instrumentation amplifier further includes a first loop capacitor and a second loop capacitor. One end of the first loop capacitor is coupled to the node between the first chopper and the fourth input capacitor, and the other end is coupled to the second input terminal of the third chopper. One end of the second loop capacitor is coupled to the node between the first chopper and the third input capacitor, and the other end is coupled to the first input terminal of the third chopper.

[0012] In one embodiment of the present invention, the multipath instrumentation amplifier further includes a third-loop capacitor and a fourth-loop capacitor. One end of the third-loop capacitor is coupled to the node between the voltage input terminal and the first input capacitor, and the other end is coupled to the node between the voltage output terminal and the inverting output terminal of the second amplifier. One end of the fourth-loop capacitor is coupled to the node between the voltage input terminal and the second input capacitor, and the other end is coupled to the node between the voltage output terminal and the non-inverting output terminal of the second amplifier.

[0013] In one embodiment of the present invention, the multipath instrumentation amplifier further includes a first capacitor, a second capacitor, a first-loop cutoff, a first-loop amplifier, a second-loop amplifier, a third capacitor, and a fourth capacitor. The input terminal of the first-loop cutoff is coupled to the inverting input terminal and the non-inverting input terminal of the fifth amplifier through the first capacitor and the second capacitor, respectively. The non-inverting input terminal and the inverting input terminal of the first-loop amplifier are coupled to the output terminal of the first-loop cutoff. The non-inverting input terminal and the inverting input terminal of the second-loop amplifier are coupled to the inverting output terminal and the non-inverting output terminal of the first-loop amplifier, respectively. The non-inverting output terminal and the inverting output terminal of the second-loop amplifier are coupled to the inverting output terminal and the non-inverting output terminal of the third amplifier, respectively. The third capacitor is coupled between the non-inverting input terminal and the inverting output terminal of the first-loop amplifier, and the fourth capacitor is coupled between the inverting input terminal and the non-inverting output terminal of the first-loop amplifier.

[0014] In one embodiment of the present invention, the multipath instrumentation amplifier further includes a first auto-zero capacitor, a first switch, a second auto-zero capacitor, a second switch, a third-loop amplifier, a fourth-loop amplifier, a third switch, a fourth switch, a fifth capacitor, a sixth capacitor, and a fifth-loop amplifier. The first switch is coupled to the first auto-zero capacitor to the inverting input terminal of the first-loop amplifier or a second reference voltage. The second switch is coupled to the second auto-zero capacitor to the non-inverting input terminal of the first-loop amplifier or the second reference voltage. The non-inverting input terminal of the third-loop amplifier is coupled to the first switch through the first auto-zero capacitor, and the inverting input terminal is coupled to the second switch through the second auto-zero capacitor. The third switch is coupled to the non-inverting output terminal of the third-loop amplifier to the non-inverting input terminal of the fourth-loop amplifier or the non-inverting input terminal of the third-loop amplifier. The fourth switch is coupled to the non-inverting output terminal of the third-loop amplifier to the inverting input terminal of the fourth-loop amplifier or the inverting input terminal of the third-loop amplifier. The fifth capacitor is coupled between the inverting output and the non-inverting input of the fourth-loop amplifier, and the sixth capacitor is coupled between the non-inverting output and the inverting input of the fourth-loop amplifier. The non-inverting and inverting inputs of the fifth-loop amplifier are respectively coupled to the inverting and non-inverting outputs of the fourth-loop amplifier, and the inverting and non-inverting outputs of the fifth-loop amplifier are respectively coupled to the non-inverting and inverting inputs of the second-loop amplifier.

[0015] In one embodiment of the present invention, the multipath instrumentation amplifier further includes a first auto-zero capacitor, a first switch, a second auto-zero capacitor, a second switch, a third-loop amplifier, a fourth-loop amplifier, a third switch, a fourth switch, and a fifth capacitor. The first switch is coupled to the first auto-zero capacitor to the inverting input terminal of the first-loop amplifier or a second reference voltage. The second switch is coupled to the second auto-zero capacitor to the non-inverting input terminal of the first-loop amplifier or the second reference voltage. The non-inverting input terminal of the third-loop amplifier is coupled to the first switch through the first auto-zero capacitor, and the inverting input terminal is coupled to the second switch through the second auto-zero capacitor. The inverting output terminal and the non-inverting output terminal of the fourth-loop amplifier are respectively coupled to the inverting input terminal and the non-inverting input terminal of the second-loop amplifier. The third switch is coupled to the inverting output terminal of the third-loop amplifier to the non-inverting input terminal of the fourth-loop amplifier or the non-inverting input terminal of the third-loop amplifier. The fourth switch is coupled to the non-inverting output terminal of the third-loop amplifier to the inverting input terminal of the fourth-loop amplifier or the inverting input terminal of the third-loop amplifier. The fifth capacitor is coupled between the inverting input and the non-inverting input of the fourth loop amplifier.

[0016] In one embodiment of the present invention, the multipath instrumentation amplifier further includes a third-loop amplifier, a second-loop cutoff, a fourth-loop amplifier, a fifth capacitor, a sixth capacitor, and a fifth-loop amplifier. The inverting input terminal of the third-loop amplifier is coupled to the node between the first capacitor and the first-loop cutoff, and the non-inverting input terminal is coupled to the node between the second capacitor and the first-loop cutoff. The non-inverting and inverting input terminals of the fourth-loop amplifier are coupled to the inverting and non-inverting output terminals of the third-loop amplifier, respectively, through the second-loop cutoff. The fifth capacitor is coupled between the inverting and non-inverting input terminals of the fourth-loop amplifier, and the sixth capacitor is coupled between the non-inverting and inverting input terminals of the fourth-loop amplifier. The non-inverting and inverting input terminals of the fifth-loop amplifier are coupled to the inverting and non-inverting output terminals of the fourth-loop amplifier, respectively, and the inverting and non-inverting output terminals of the fifth-loop amplifier are coupled to the non-inverting and inverting input terminals of the second-loop amplifier, respectively.

[0017] In one embodiment of the present invention, the multipath instrumentation amplifier further includes a first nested cutter and a second nested cutter. One end of a third capacitor is coupled to the non-inverting input terminal of the first loop amplifier through the first nested cutter, and the other end of the third capacitor is coupled to the inverting output terminal of the first loop amplifier through the second nested cutter. One end of a fourth capacitor is coupled to the inverting input terminal of the first loop amplifier through the first nested cutter, and the other end of the fourth capacitor is coupled to the non-inverting output terminal of the first loop amplifier through the second nested cutter.

[0018] In one embodiment of the present invention, the multipath instrumentation amplifier further includes a first capacitor, a second capacitor, a first buffer, a first loop cutter, a second buffer, a third capacitor, and a loop amplifier. The inverting input terminal and the non-inverting input terminal of the first buffer are respectively coupled to the inverting input terminal and the non-inverting input terminal of the fifth amplifier through the first capacitor and the second capacitor. The input terminal of the first loop cutter is respectively coupled to the non-inverting output terminal and the inverting output terminal of the first buffer. The inverting input terminal and the non-inverting input terminal of the second buffer are respectively coupled to the output terminal of the first loop cutter. The third capacitor is coupled between the non-inverting output terminal and the inverting output terminal of the second buffer. The non-inverting input terminal and the inverting input terminal of the loop amplifier are respectively coupled to the non-inverting output terminal and the inverting output terminal of the second buffer, and the non-inverting output terminal and the inverting output terminal of the loop amplifier are respectively coupled to the non-inverting output terminal and the inverting output terminal of the third amplifier.

[0019] In one embodiment of the present invention, the multipath instrumentation amplifier further includes a buffer, wherein its inverting input terminal and non-inverting input terminal are respectively coupled to a first capacitor and a second capacitor, and the non-inverting output terminal and inverting output terminal of the buffer are respectively coupled to the input terminal of a first loop cutoff.

[0020] In one embodiment of the present invention, the multipath instrumentation amplifier further includes a fourth cutoff, the input terminal of which is coupled to the non-inverting input terminal and the inverting input terminal of the third amplifier respectively, and the output terminal of the fourth cutoff is coupled to the non-inverting input terminal and the inverting input terminal of the first amplifier respectively.

[0021] Based on the above, the multi-path instrumentation amplifier uses a high-frequency amplification circuit and a capacitor to form a feedback path to reduce voltage ripple at the voltage output terminal, thereby increasing stability and accuracy.

[0022] To enable your review committee to have a better understanding of the structural features and effects achieved by the present invention, the following description is provided, accompanied by preferred embodiment diagrams and detailed explanation:

Implementation Method

[0023] Embodiments of the present invention will be further explained below with reference to the accompanying drawings. Wherever possible, the same reference numerals in the drawings and description represent the same or similar components. In the drawings, shapes and thicknesses may be exaggerated for simplification and convenience. It is understood that elements not specifically shown in the drawings or described in the description are forms known to those skilled in the art. Those skilled in the art can make various changes and modifications based on the content of this invention.

[0024] Unless otherwise specified, certain conditional clauses or words, such as "can," "could," "might," or "may," are generally intended to express features, elements, or steps that are present in the embodiments of this invention, but may also be interpreted as features, elements, or steps that may not be required. In other embodiments, these features, elements, or steps may be unnecessary.

[0025] The description of “one embodiment” or “an embodiment” in the following text refers to a specific element, structure, or feature associated with at least one embodiment. Therefore, the multiple descriptions of “one embodiment” or “an embodiment” appearing in various places below do not refer to the same embodiment. Furthermore, specific components, structures, and features in one or more embodiments may be combined in a suitable manner. It is worth noting that the following drawings are not drawn to scale, and these drawings are for illustrative purposes only.

[0026] Certain terms are used in the specification and claims to refer to specific elements. However, those skilled in the art will understand that the same element may be referred to by different names. The specification and claims do not distinguish elements by differences in name, but by differences in function. The term "comprising" as used in the specification and claims is an open-ended term and should be interpreted as "comprising but not limited to". In addition, "coupled" here includes any direct and indirect means of connection. Therefore, if the text describes a first element coupled to a second element, it means that the first element can be directly connected to the second element by electrical connection or signal connection such as wireless transmission or optical transmission, or indirectly electrically or signal connected to the second element by other elements or connection means.

[0027] The disclosure is specifically described by the following examples, which are merely illustrative. Various modifications and refinements can be made by those skilled in the art without departing from the spirit and scope of this disclosure. Therefore, the scope of protection of this disclosure shall be determined by the appended claims. Throughout the specification and claims, unless explicitly stated otherwise, the words “a” and “the” include statements containing “a or at least one” of the element or component. Furthermore, as used in this disclosure, the singular article also includes statements of a plurality of elements or components unless clearly excluded from the specific context. Moreover, when applied in this description and throughout the claims below, unless explicitly stated otherwise, “in which” may include both “in which” and “on which”. The terms used throughout the specification and claims, unless otherwise specified, generally have their ordinary meaning in the art, in the content of this disclosure, and in the specific context. Certain terms used to describe this disclosure will be discussed below or elsewhere in this specification to provide additional guidance to practitioners in describing this disclosure. Examples throughout this specification, including examples of any terms discussed herein, are for illustrative purposes only and do not limit the scope or meaning of this disclosure or any illustrative terms. Similarly, this disclosure is not limited to the various embodiments set forth in this specification.

[0028] In the following description, a multipath instrumentation amplifier will be described, which employs a high-frequency amplification circuit and uses capacitors to form a feedback path to reduce voltage ripple at the voltage output terminal, thereby increasing stability and accuracy.

[0029] Figure 1 is a schematic diagram of a multipath instrumentation amplifier according to a first embodiment of the present invention. Referring to Figure 1, a multipath instrumentation amplifier is described below, which has a voltage input terminal and a voltage output terminal. The multipath instrumentation amplifier includes a low-frequency amplifier circuit 10 and a high-frequency amplifier circuit 11. The low-frequency amplifier circuit 10 and the high-frequency amplifier circuit 11 are coupled between the voltage input terminal and the voltage output terminal. The high-frequency amplifier circuit 11 includes a first amplifier 12, a second amplifier 13, a first input resistor 14, a first input capacitor 15, a second input resistor 16, a second input capacitor 17, a first feedback capacitor 18, and a second feedback capacitor 19. The first amplifier 12 and the second amplifier 13 may be, but are not limited to, transconductance amplifiers. The inverting output terminal and the non-inverting output terminal of the first amplifier 12 are respectively coupled to the non-inverting input terminal and the inverting input terminal of the second amplifier 13, and the non-inverting output terminal and the inverting output terminal of the second amplifier 13 are coupled to the voltage output terminal. A first input resistor 14 and a first input capacitor 15 are connected in series between a first reference voltage V1 and the voltage input terminal. The node between the first input resistor 14 and the first input capacitor 15 is coupled to the non-inverting input terminal of the first amplifier 12. A second input resistor 16 and a second input capacitor 17 are connected in series between the first reference voltage V1 and the voltage input terminal. The node between the second input resistor 16 and the second input capacitor 17 is coupled to the inverting input terminal of the first amplifier 12. A first feedback capacitor 18 is coupled between the voltage output terminal and the inverting input terminal of the first amplifier 12. A second feedback capacitor 19 is coupled between the voltage output terminal and the non-inverting input terminal of the first amplifier 12.

[0030] The low-frequency amplifier circuit 10 may include, but is not limited to, a third amplifier 20, a first chopper 21, a third input capacitor 22, a fourth input capacitor 23, a second chopper 24, a fourth amplifier 25, a fifth amplifier 26, a third chopper 27, a third feedback capacitor 28, a first feedback resistor 29, a fourth feedback capacitor 30, and a second feedback resistor 31. The third amplifier 20, fourth amplifier 25, and fifth amplifier 26 may be, but are not limited to, transconductance amplifiers. The input terminal of the first chopper 21 is coupled to a voltage input terminal, and the output terminal of the first chopper 21 is coupled to the non-inverting input terminal and the inverting input terminal of the third amplifier 20 through the third input capacitor 22 and the fourth input capacitor 23, respectively. The input terminal of the second chopper 24 is coupled to the inverting output terminal and the non-inverting output terminal of the third amplifier 20, respectively. The non-inverting input terminal and the inverting input terminal of the fourth amplifier 25 are coupled to the output terminal of the second chopper 24. The non-inverting and inverting inputs of the fifth amplifier 26 are respectively coupled to the inverting and non-inverting outputs of the fourth amplifier 25. The inverting and non-inverting outputs of the fifth amplifier 26 are respectively coupled to the non-inverting and inverting inputs of the second amplifier 13. The third cutoff 27 has a first input and a second input, and its output is coupled to a voltage output. The third feedback capacitor 28 and the first feedback resistor 29 are connected in parallel and coupled between the first input of the third cutoff 27 and the inverting input of the third amplifier 20. The fourth feedback capacitor 30 and the second feedback resistor 31 are connected in parallel and coupled between the second input of the third cutoff 27 and the non-inverting input of the third amplifier 20.

[0031] Figure 2 is a schematic diagram of a cutoff switch according to an embodiment of the present invention. As shown in Figure 2, the cutoff switch used in a multipath instrumentation amplifier has two input terminals and two output terminals, and includes a first electronic switch SW1, a second electronic switch SW2, a third electronic switch SW3, and a fourth electronic switch SW4. The control terminals of the first electronic switch SW1 and the third electronic switch SW3 are coupled to a first clock signal CK1, and the control terminals of the second electronic switch SW2 and the fourth electronic switch SW4 are coupled to a second clock signal CK2. The first clock signal CK1 and the second clock signal CK2 are out of phase, and their frequencies are the same. One end of the first electronic switch SW1 is coupled to one input terminal and one end of the second electronic switch SW2, and the other end of the first electronic switch SW1 is coupled to one output terminal and one end of the fourth electronic switch SW4. The other end of the second electronic switch SW2 is coupled to another output terminal and one end of the third electronic switch SW3. The other end of the third electronic switch SW3 is coupled to another input terminal and the other end of the fourth electronic switch SW4. All the cutoffs in the multipath instrumentation amplifier correspond to the same frequency fCH.

[0032] Figure 3 is a Bode magnitude plot of a low-frequency amplifier circuit, a high-frequency amplifier circuit, and a multi-path instrumentation amplifier according to an embodiment of the present invention. Referring to Figures 1 and 3, an input voltage Vin is coupled to the voltage input terminal. The low-frequency amplifier circuit 10 and the high-frequency amplifier circuit 11 amplify the input voltage Vin and transmit the amplified input voltage Vin to the voltage output terminal to generate an output voltage Vout. The high-frequency amplifier circuit 11 uses a first feedback capacitor 18 and a second feedback capacitor 19 to form a negative feedback path to reduce voltage ripple at the voltage output terminal, thereby increasing the stability and accuracy of the multi-path instrumentation amplifier. In Figure 3, the upper inset represents the low-frequency amplifier circuit 10, the middle inset represents the high-frequency amplifier circuit 11, and the lower inset represents the multi-path instrumentation amplifier, where f represents the frequency. The gain of the multipath instrumentation amplifier is determined by the capacitance ratio of the first input capacitor 15, the second input capacitor 17, the third input capacitor 22, the fourth input capacitor 23, the first feedback capacitor 18, the second feedback capacitor 19, the third feedback capacitor 28, and the fourth feedback capacitor 30. The frequency response of the low-frequency amplifier circuit 10 begins to decrease at low frequencies. If the cutoff frequency of the high-frequency amplifier circuit 11 is lower than the -3 dB frequency of the low-frequency amplifier circuit 10, the overall frequency response will remain flat. This is because when the frequency response of the low-frequency amplifier circuit 10 begins to decrease, the function of the low-frequency amplifier circuit 10 is taken over by the function of the high-frequency amplifier circuit 11. In other words, the high-frequency amplifier circuit 11 is a feedforward path used to compensate for the bandwidth limitations of the low-frequency amplifier circuit 10. Finally, the overall frequency response will follow the frequency response of the high-frequency amplifier circuit 11 at high frequencies to determine the overall -3 dB bandwidth, forming a high-bandwidth cutoff amplifier. Although the overall bandwidth is increased by the high-frequency amplifier circuit 11, the flicker noise and offset voltage of the high-frequency amplifier circuit 11 must be removed. Therefore, an additional feedback path will appear between the high-frequency amplifier circuit 11 and the low-frequency amplifier circuit 10 to establish an offset-stabilized circuit. The offset voltage of the first amplifier 12 is coupled to the low-frequency amplifier circuit 10 at the output node through the third chopper 27, the third feedback capacitor 28, the first feedback resistor 29, the fourth feedback capacitor 30, and the second feedback resistor 31. Then, the aforementioned offset voltage is fed back to the auxiliary input path of the first amplifier 12, namely the fifth amplifier 26. Due to the negative feedback, the offset voltage of the first amplifier 12 will be stabilized by the gains of the third amplifier 20, the fourth amplifier 25, and the fifth amplifier 26, and the noise of the high-frequency amplifier circuit 11 will also be suppressed by the same principle.

[0033] Although the frequency response of the multipath instrumentation amplifier is determined by the high-frequency amplifier circuit 11, the low-frequency amplifier circuit 10 should maintain stability before being taken over by the high-frequency amplifier circuit 11. To achieve stability compensation and ripple suppression, the multipath instrumentation amplifier may further include a resistor-capacitor circuit 32, which is coupled to the inverting input, non-inverting input, inverting output, and non-inverting output of the fourth amplifier 25 and the second amplifier 13, and performs frequency compensation for the low-frequency amplifier circuit 10 and the high-frequency amplifier circuit 11. The resistor-capacitor circuit 32 may be, but is not limited to, a low-pass filter. In some embodiments of the present invention, the resistor-capacitor circuit 32 may include, but is not limited to, a first compensation capacitor 33, a second compensation capacitor 34, a third compensation capacitor 35, a first compensation resistor 36, a fourth compensation capacitor 37, a second compensation resistor 38, a fifth compensation capacitor 39, and a sixth compensation capacitor 40. The first compensation capacitor 33 is coupled between the non-inverting output terminal of the second amplifier 13 and the inverting input terminal of the fourth amplifier 25. The second compensation capacitor 34 is coupled between the inverting output terminal of the second amplifier 13 and the non-inverting input terminal of the fourth amplifier 25. The third compensation capacitor 35 is connected in series with the first compensation resistor 36 and is also coupled between the inverting output terminal and the non-inverting input terminal of the fourth amplifier 25. The fourth compensation capacitor 37 is connected in series with the second compensation resistor 38 and is also coupled between the non-inverting output terminal and the inverting input terminal of the fourth amplifier 25. The fifth compensation capacitor 39 is coupled between the non-inverting input terminal and the inverting output terminal of the second amplifier 13. The sixth compensation capacitor 40 is coupled between the inverting input terminal and the non-inverting output terminal of the second amplifier 13.

[0034] To amplify the voltage signal, the input impedance of the multipath instrumentation amplifier should be high enough to receive the input signal. However, although the low-frequency amplifier circuit 10 can amplify the DC signal, the DC impedance will be reduced due to the chopper and the input capacitor. In addition, the input capacitor will result in low impedance at high frequencies in the high-frequency amplifier circuit 11. To solve this problem, the multipath instrumentation amplifier may further include a first-loop capacitor 41, a second-loop capacitor 42, a third-loop capacitor 43, and a fourth-loop capacitor 44.

[0035] The first loop capacitor 41 and the second loop capacitor 42 are used to eliminate the non-ideal input current caused by the first cutoff capacitor 21, the third input capacitor 22, and the fourth input capacitor 23 at low frequencies. One end of the first loop capacitor 41 is coupled to the node between the first cutoff capacitor 21 and the fourth input capacitor 23, and the other end is coupled to the second input terminal of the third cutoff capacitor 27. One end of the second loop capacitor 42 is coupled to the node between the first cutoff capacitor 21 and the third input capacitor 22, and the other end is coupled to the first input terminal of the third cutoff capacitor 27.

[0036] The third-loop capacitor 43 and the fourth-loop capacitor 44 are used to eliminate the non-ideal input current caused by the first input capacitor 15 and the second input capacitor 17 at high frequencies. One end of the third-loop capacitor 43 is coupled to the node between the voltage input terminal and the first input capacitor 15, and the other end is coupled to the node between the voltage output terminal and the inverting output terminal of the second amplifier 13. One end of the fourth-loop capacitor 44 is coupled to the node between the voltage input terminal and the second input capacitor 17, and the other end is coupled to the node between the voltage output terminal and the non-inverting output terminal of the second amplifier 13.

[0037] Assume that the capacitances of the first input capacitor 15, the second input capacitor 17, the third input capacitor 22, and the fourth input capacitor 23 are the same, denoted as CIN; and the capacitances of the first loop capacitor 41, the second loop capacitor 42, the third loop capacitor 43, and the fourth loop capacitor 44 are the same, denoted as CPFL. At low frequencies, due to the effects of the third input capacitor 22, the fourth input capacitor 23, the first loop capacitor 41, and the second loop capacitor 42, Zin = 1 / {2fCH[CIN-CPFL (ACL,CCCIA-1)]}. At high frequencies, due to the effects of the first input capacitor 15, the second input capacitor 17, the third loop capacitor 43, and the fourth loop capacitor 44, Zin = 1 / {[CIN-CPFL (ACL,CCIA-1)]}. Zin represents the input impedance of the multipath instrumentation amplifier, ACL,CCCIA represents the closed-loop gain of the low-frequency amplifier circuit 10, ACL,CCIA represents the closed-loop gain of the high-frequency amplifier circuit 11, and AMCCCIA represents the gain of the multipath instrumentation amplifier. Therefore, when Zin is infinite and ACL,CCCIA = ACL,CCIA = AMCCCIA, CPFL = CIN / (AMCCCIA-1).

[0038] The high-frequency amplifier circuit 11 causes ripple suppression, so it can also be called an automatic ripple suppression circuit. Because the low-frequency amplifier circuit 10 uses a chopper modulation technique, chopper ripple will exist at the voltage output terminal. The chopper ripple at the voltage output terminal will only couple to the high-frequency amplifier circuit 11, and then return to the voltage output terminal through the first amplifier 12 and the second amplifier 13. The reason why the chopper ripple will not couple to the low-frequency amplifier circuit 10 is due to the third chopper 27. The third chopper 27 modulates the chopper ripple to a DC state, and the DC signal will be blocked by the infinite impedance of the third feedback capacitor 28 and the fourth feedback capacitor 30. Therefore, the chopper ripple will only couple to the high-frequency amplifier circuit 11, making the high-frequency amplifier circuit 11 like the ripple suppression circuit of the low-frequency amplifier circuit 10. The advantage of the automatic ripple suppression circuit is not only that it can reduce ripple without adding additional circuitry, but also that it can use the offset stabilization circuit to suppress the noise and non-ideal effects of the offset voltage of the ripple suppression circuit. Furthermore, the multipath instrumentation amplifier utilizes the basic principles of capacitors and the modulation technique of choppers to clearly distinguish the feedback paths of different signals. For example, the output ripple will follow the path of the automatic ripple suppression circuit, while the offset voltage of the first amplifier 12 will follow the path of the offset stabilization circuit. Assume L represents the gain of the automatic ripple suppression circuit, Ro1 and Ro2 are the output resistance values ​​of the first amplifier 12 and the second amplifier 13 respectively, Gm1 and Gm2 are the transconductances of the first amplifier 12 and the second amplifier 13 respectively, and the first feedback capacitor 18 and the second feedback capacitor 19 have the same capacitance, denoted as CFB, where CIN >> CFB. Due to the effects of the first feedback capacitor 18, the second feedback capacitor 19, the first input capacitor 15, and the second input capacitor 17, ACL,CCIA = CIN / CFB. Due to the effects of the first amplifier 12 and the second amplifier 13, AOL,CCIA = Gm1 × Ro1 × Gm2 × Ro2, where AOL,CCIA represents the open-loop gain of the high-frequency amplifier circuit 11. Because of the effects of the first feedback capacitor 18, the second feedback capacitor 19, the first input capacitor 15, the second input capacitor 17, the first amplifier 12, and the second amplifier 13, L≈CFB×Gm1×Ro1×Gm2×Ro2 / (CIN+CFB) ≈CFB×Gm1×Ro1×Gm2×Ro2 / CIN=AOL,CCIA / ACL,CCIA. Therefore, L is proportional to AOL,CCIA.

[0039] Figure 4 is a schematic diagram of a ripple suppression circuit according to a first embodiment of the present invention. Referring to Figure 4, when a notch appears in the frequency response of the amplifier, although the ripple from the cutter can be suppressed, the notch will cause unwanted ringing in the step response. To solve this problem, the multipath instrumentation amplifier only inserts one ripple suppression circuit RRL1 into the low-frequency amplifier circuit 10. Therefore, the overall frequency response of the multipath instrumentation amplifier will not have a notch, and the ripple suppression circuit RRL1 also retains the function of suppressing the ripple from the cutter. The ripple suppression circuit RRL1 includes a first capacitor 45, a second capacitor 46, a first loop cutter 47, a first loop amplifier 48, a second loop amplifier 49, a third capacitor 50, and a fourth capacitor 51. The first loop amplifier 48 and the second loop amplifier 49 can be, but are not limited to, transconductance amplifiers. The input terminals of the first loop cutter 47 are coupled to the inverting and non-inverting input terminals of the fifth amplifier 26 via the first capacitor 45 and the second capacitor 46, respectively. The non-inverting and inverting input terminals of the first loop amplifier 48 are coupled to the output terminals of the first loop cutter 47. The non-inverting and inverting input terminals of the second loop amplifier 49 are coupled to the inverting and non-inverting output terminals of the first loop amplifier 48, respectively. The non-inverting and inverting output terminals of the second loop amplifier 49 are coupled to the inverting and non-inverting output terminals of the third amplifier 20, respectively. The third capacitor 50 is coupled between the non-inverting and inverting output terminals of the first loop amplifier 48, and the fourth capacitor 51 is coupled between the inverting and non-inverting output terminals of the first loop amplifier 48.

[0040] However, the offset voltage of the ripple suppression circuit RRL1 will generate additional residual ripple at the voltage output terminal, which cannot be suppressed. To solve this problem, an offset compensation circuit is designed.

[0041] Figure 5 is a schematic diagram of the offset compensation circuit according to the first embodiment of the present invention. Referring to Figure 5, the multipath instrumentation amplifier further includes an offset compensation circuit OCL1. The offset compensation circuit OCL1 includes a first auto-zero capacitor 52, a first switch 53, a second auto-zero capacitor 54, a second switch 55, a third circuit amplifier 56, a fourth circuit amplifier 57, a third switch 58, a fourth switch 59, a fifth capacitor 60, a sixth capacitor 61, and a fifth circuit amplifier 62. The third circuit amplifier 56, the fourth circuit amplifier 57, and the fifth circuit amplifier 62 may be, but are not limited to, transconductance amplifiers. The first switch 53 is coupled to the first auto-zero capacitor 52 to the inverting input terminal of the first circuit amplifier 48 or a second reference voltage V2. The second switch 55 is coupled to the second auto-zero capacitor 54 to the non-inverting input terminal of the first circuit amplifier 48 or the second reference voltage V2. The non-inverting input of the third-loop amplifier 56 is coupled to the first switch 53 through the first auto-zero capacitor 52, and the inverting input is coupled to the second switch 55 through the second auto-zero capacitor 54. The third switch 58 couples the inverting output of the third-loop amplifier 56 to either the non-inverting input of the fourth-loop amplifier 57 or the non-inverting input of the third-loop amplifier 56. The fourth switch 59 couples the non-inverting output of the third-loop amplifier 56 to either the inverting input of the fourth-loop amplifier 57 or the inverting input of the third-loop amplifier 56. The fifth capacitor 60 is coupled between the inverting output and the non-inverting input of the fourth-loop amplifier 57. The sixth capacitor 61 is coupled between the non-inverting output and the inverting input of the fourth-loop amplifier 57. The non-inverting input and inverting input of the fifth circuit amplifier 62 are respectively coupled to the inverting output and non-inverting output of the fourth circuit amplifier 57. The inverting output and non-inverting output of the fifth circuit amplifier 62 are respectively coupled to the non-inverting input and inverting input of the second circuit amplifier 49.

[0042] Figure 6 is a schematic diagram of an offset compensation circuit according to a second embodiment of the present invention. Referring to Figure 6, the multipath instrumentation amplifier further includes an offset compensation circuit OCL2. The offset compensation circuit OCL2 includes a first auto-zero capacitor 63, a first switch 64, a second auto-zero capacitor 65, a second switch 66, a third circuit amplifier 67, a fourth circuit amplifier 68, a third switch 69, a fourth switch 70, and a fifth capacitor 71. The third circuit amplifier 67 and the fourth circuit amplifier 68 may be, but are not limited to, transconductance amplifiers. The first switch 64 is coupled to the first auto-zero capacitor 63 to the inverting input terminal of the first circuit amplifier 48 or a second reference voltage V2. The second switch 66 is coupled to the second auto-zero capacitor 65 to the non-inverting input terminal of the first circuit amplifier 48 or the second reference voltage V2. The non-inverting input terminal of the third circuit amplifier 67 is coupled to the first switch 64 through the first auto-zero capacitor 63, and the inverting input terminal is coupled to the second switch 66 through the second auto-zero capacitor 65. The inverting and non-inverting outputs of the fourth-loop amplifier 68 are coupled to the inverting and non-inverting inputs of the second-loop amplifier 49, respectively. The third switch 69 is coupled from the inverting output of the third-loop amplifier 67 to either the non-inverting input of the fourth-loop amplifier 68 or the non-inverting input of the third-loop amplifier 67. The fourth switch 70 is coupled from either the non-inverting output of the third-loop amplifier 67 to either the inverting input of the fourth-loop amplifier 68 or the inverting input of the third-loop amplifier 67. The fifth capacitor 71 is coupled between the inverting and non-inverting inputs of the fourth-loop amplifier 68.

[0043] Figure 7 is a schematic diagram of the offset compensation circuit according to the third embodiment of the present invention. Referring to Figure 7, the multipath instrumentation amplifier further includes an offset compensation circuit OCL3. The offset compensation circuit OCL3 includes a third circuit amplifier 72, a second circuit cutter 73, a fourth circuit amplifier 74, a fifth capacitor 75, a sixth capacitor 76, and a fifth circuit amplifier 77. The third circuit amplifier 72, the fourth circuit amplifier 74, and the fifth circuit amplifier 77 may be, but are not limited to, transconductance amplifiers. The inverting input terminal of the third circuit amplifier 72 is coupled to the node between the first capacitor 45 and the first circuit cutter 47, and the non-inverting input terminal of the third circuit amplifier 72 is coupled to the node between the second capacitor 46 and the first circuit cutter 47. The non-inverting input terminal and the inverting input terminal of the fourth circuit amplifier 74 are coupled to the inverting output terminal and the non-inverting output terminal of the third circuit amplifier 72 respectively through the second circuit cutter 73. The fifth capacitor 75 is coupled between the inverting output and the non-inverting input of the fourth-loop amplifier 74, and the sixth capacitor 76 is coupled between the non-inverting output and the inverting input of the fourth-loop amplifier 74. The non-inverting input and the inverting input of the fifth-loop amplifier 77 are respectively coupled to the inverting output and the non-inverting output of the fourth-loop amplifier 74, and the inverting output and the non-inverting output of the fifth-loop amplifier 77 are respectively coupled to the non-inverting input and the inverting input of the second-loop amplifier 49.

[0044] Figure 8 is a schematic diagram of a ripple suppression circuit according to a second embodiment of the present invention. Please refer to Figure 8. To further reduce the ripple voltage at the voltage output terminal, compared with the embodiment in Figure 4, the ripple suppression circuit RRL2 in Figure 8 further includes a first nested cutoff 78 and a second nested cutoff 79. One end of the third capacitor 50 is coupled to the non-inverting input terminal of the first loop amplifier 48 through the first nested cutoff 78, and the other end of the third capacitor 50 is coupled to the inverting output terminal of the first loop amplifier 48 through the second nested cutoff 79. One end of the fourth capacitor 51 is coupled to the inverting input terminal of the first loop amplifier 48 through the first nested cutoff 78, and the other end of the fourth capacitor 51 is coupled to the non-inverting output terminal of the first loop amplifier 48 through the second nested cutoff 79. The first nested cutoff 78 and the second nested cutoff 79 are used to reduce the effect caused by the offset voltage of the first loop amplifier 48. The embodiment in Figure 8 can be combined with the embodiment in Figure 4, or with the embodiments in Figure 5, Figure 6 or Figure 7.

[0045] Figure 9 is a schematic diagram of a ripple suppression circuit according to a third embodiment of the present invention. Please refer to Figure 9. Because the offset voltage of the ripple suppression circuit RRL1 in Figure 4 will generate additional residual ripple at the voltage output terminal, which cannot be suppressed, a ripple suppression circuit RRL3 is provided to replace the ripple suppression circuit RRL1 in Figure 4. The ripple suppression circuit RRL3 includes a first capacitor 80, a second capacitor 81, a first buffer 82, a first loop cutter 83, a second buffer 84, a third capacitor 85, and a loop amplifier 86. The loop amplifier 86 may be, but is not limited to, a transconductance amplifier. The inverting input terminal and the non-inverting input terminal of the first buffer 82 are coupled to the inverting input terminal and the non-inverting input terminal of the fifth amplifier 26 through the first capacitor 80 and the second capacitor 81, respectively. The input terminals of the first loop cutter 83 are coupled to the non-inverting and inverting output terminals of the first buffer 82, respectively. The inverting and non-inverting input terminals of the second buffer 84 are coupled to the output terminals of the first loop cutter 83, respectively. The third capacitor 85 is coupled between the non-inverting and inverting output terminals of the second buffer 84. The third capacitor 85 can integrate the received signal to avoid the offset voltage output of the ripple suppression circuit RRL3. The non-inverting and inverting input terminals of the loop amplifier 86 are coupled to the non-inverting and inverting output terminals of the second buffer 84, respectively. The non-inverting and inverting output terminals of the loop amplifier 86 are coupled to the non-inverting and inverting output terminals of the third amplifier 20, respectively. The embodiment in Figure 9 can be combined with the embodiment in Figure 4, or with the embodiments in Figures 5, 6, or 7.

[0046] Figure 10 is a schematic diagram of a ripple suppression circuit according to a fourth embodiment of the present invention. Please refer to Figure 10. To avoid deteriorating the ripple voltage at the voltage output terminal, compared with the embodiment in Figure 4, the ripple suppression circuit RRL4 in Figure 10 further includes a buffer 87, whose inverting input terminal and non-inverting input terminal are respectively coupled to a first capacitor 45 and a second capacitor 46, and whose non-inverting output terminal and inverting output terminal are respectively coupled to the input terminal of a first loop cutoff 47. The embodiment in Figure 10 can be combined with the embodiment in Figure 4, or with the embodiments in Figures 5, 6, or 7.

[0047] Figure 11 is a schematic diagram of a multipath instrumentation amplifier according to a second embodiment of the present invention. Please refer to Figure 11. Compared with the embodiment in Figure 1, the multipath instrumentation amplifier in Figure 11 further includes a fourth cutoff 88, the input of which is coupled to the non-inverting input and the inverting input of the third amplifier 20, respectively, and the output of the fourth cutoff 88 is coupled to the non-inverting input and the inverting input of the first amplifier 12, respectively. The fourth cutoff 88 is used to rectify the feedback ripple at the voltage input and to compensate for the offset voltage of the first amplifier 12 without requiring automatic-zeroing of the first amplifier 12. The embodiment in Figure 11 can be combined with the embodiments in Figures 5, 6, 7, 8, 9, or 10.

[0048] According to the embodiments provided above, the multi-path instrumentation amplifier uses a high-frequency amplification circuit and a capacitor to form a feedback path to reduce voltage ripple at the voltage output terminal, thereby increasing stability and accuracy.

[0049] The above description is only a preferred embodiment of the present invention and is not intended to limit the scope of the present invention. Therefore, all equivalent changes and modifications made in accordance with the shape, structure, features and spirit described in the claims of the present invention should be included in the scope of the claims of the present invention. [Simplified Explanation of the Diagram]

[0050] Figure 1 is a schematic diagram of a multipath instrumentation amplifier according to a first embodiment of the present invention. Figure 2 is a schematic diagram of a cutoff circuit according to an embodiment of the present invention. Figure 3 is a Bode magnitude plot of a low-frequency amplifier circuit, a high-frequency amplifier circuit, and a multipath instrumentation amplifier according to an embodiment of the present invention. Figure 4 is a schematic diagram of a ripple suppression circuit according to a first embodiment of the present invention. Figure 5 is a schematic diagram of an offset compensation circuit according to a first embodiment of the present invention. Figure 6 is a schematic diagram of an offset compensation circuit according to a second embodiment of the present invention. Figure 7 is a schematic diagram of an offset compensation circuit according to a third embodiment of the present invention. Figure 8 is a schematic diagram of a ripple suppression circuit according to a second embodiment of the present invention. Figure 9 is a schematic diagram of a ripple suppression circuit according to a third embodiment of the present invention. Figure 10 is a schematic diagram of a ripple suppression circuit according to a fourth embodiment of the present invention. Figure 11 is a schematic diagram of a multipath instrumentation amplifier according to a second embodiment of the present invention.

Claims

1. A multipath instrumentation amplifier having a voltage input terminal and a voltage output terminal, the multipath instrumentation amplifier comprising: A low-frequency amplifier circuit and a high-frequency amplifier circuit are coupled between a voltage input terminal and a voltage output terminal. The voltage input terminal is coupled to an input voltage. The low-frequency amplifier circuit and the high-frequency amplifier circuit are used to amplify the input voltage and transmit the amplified input voltage to the voltage output terminal. The high-frequency amplifier circuit is used to reduce voltage ripple on the voltage output terminal. The high-frequency amplifier circuit includes: a first amplifier and a second amplifier. The inverting output terminal and the non-inverting output terminal of the first amplifier are respectively coupled to the non-inverting input terminal and the inverting input terminal of the second amplifier. The non-inverting output terminal and the inverting output terminal of the second amplifier are coupled to the voltage output terminal. A first input resistor and a first input capacitor are connected in series between a first reference voltage and the voltage input terminal. The node between the first input resistor and the first input capacitor is coupled to the non-inverting input terminal of the first amplifier. A second input resistor and a second input capacitor are connected in series between the first reference voltage and the voltage input terminal, and the node between the second input resistor and the second input capacitor is coupled to the inverting input terminal of the first amplifier; a first feedback capacitor is coupled between the voltage output terminal and the inverting input terminal of the first amplifier; and a second feedback capacitor is coupled between the voltage output terminal and the non-inverting input terminal of the first amplifier.

2. The multipath instrumentation amplifier as described in claim 1, wherein the low-frequency amplification circuit includes: A third amplifier; A first chopper, the input of which is coupled to the voltage input; A third input capacitor and a fourth input capacitor are provided, and the output terminal of the first chopper is coupled to the non-inverting input terminal and the inverting input terminal of the third amplifier through the third input capacitor and the fourth input capacitor, respectively; a second chopper is provided, and its input terminals are coupled to the inverting output terminal and the non-inverting output terminal of the third amplifier, respectively; a fourth amplifier is provided, and its non-inverting input terminal and the inverting input terminal are coupled to the output terminal of the second chopper; a fifth amplifier is provided, and its non-inverting input terminal and the inverting input terminal are coupled to the inverting output terminal and the non-inverting output terminal of the fourth amplifier, respectively, and the inverting output terminal and the non-inverting output terminal of the fifth amplifier are coupled to the non-inverting input terminal and the inverting input terminal of the second amplifier, respectively; a third chopper is provided, and it has a first input terminal and a second input terminal, and the output terminal of the third chopper is coupled to the voltage output terminal; A third feedback capacitor and a first feedback resistor are connected in parallel and coupled between the first input terminal of the third cutoff and the inverting input terminal of the third amplifier; and a fourth feedback capacitor and a second feedback resistor are connected in parallel and coupled between the second input terminal of the third cutoff and the non-inverting input terminal of the third amplifier.

3. The multipath instrumentation amplifier as described in claim 2 further includes a resistor-capacitor circuit coupled to the inverting input, non-inverting input, inverting output and non-inverting output of the fourth amplifier and the second amplifier, and used to perform frequency compensation on the low-frequency amplifier circuit and the high-frequency amplifier circuit.

4. The multipath instrumentation amplifier as described in claim 3, wherein the resistor-capacitor circuit is a low-pass filter.

5. The multipath instrumentation amplifier as described in claim 3, wherein the resistor-capacitor circuit comprises: A first compensation capacitor is coupled between the non-inverting output terminal of the second amplifier and the inverting input terminal of the fourth amplifier; A second compensation capacitor is coupled between the inverting output terminal of the second amplifier and the non-inverting input terminal of the fourth amplifier; a third compensation capacitor and a first compensation resistor are connected in series and coupled between the inverting output terminal and the non-inverting input terminal of the fourth amplifier; a fourth compensation capacitor and a second compensation resistor are connected in series and coupled between the non-inverting output terminal and the inverting input terminal of the fourth amplifier; a fifth compensation capacitor is coupled between the non-inverting input terminal and the inverting output terminal of the second amplifier; and a sixth compensation capacitor is coupled between the inverting input terminal and the non-inverting output terminal of the second amplifier.

6. The multipath instrumentation amplifier as described in claim 2, further comprising: A first loop capacitor, one end of which is coupled to the node between the first chopper and the fourth input capacitor, and the other end of which is coupled to the second input terminal of the third chopper; And a second loop capacitor, one end of which is coupled to the node between the first chopper and the third input capacitor, and the other end of which is coupled to the first input terminal of the third chopper.

7. The multipath instrumentation amplifier as described in claim 6, further comprising: A third-loop capacitor, one end of which is coupled to the node between the voltage input terminal and the first input capacitor, and the other end of which is coupled to the node between the voltage output terminal and the inverting output terminal of the second amplifier; And a fourth circuit capacitor, one end of which is coupled to the node between the voltage input terminal and the second input capacitor, and the other end of which is coupled to the node between the voltage output terminal and the non-inverting output terminal of the second amplifier.

8. The multipath instrumentation amplifier as described in claim 2, further comprising: A first capacitor and a second capacitor; A first-loop cutoff circuit, the input terminals of which are coupled to the inverting input terminal and the non-inverting input terminal of the fifth amplifier through the first capacitor and the second capacitor, respectively; a first-loop amplifier, the non-inverting input terminal and the inverting input terminal of which are coupled to the output terminal of the first-loop cutoff circuit; a second-loop amplifier, the non-inverting input terminal and the inverting input terminal of which are coupled to the inverting output terminal and the non-inverting output terminal of the first-loop amplifier, respectively, and the non-inverting output terminal and the inverting output terminal of the second-loop amplifier are coupled to the inverting output terminal and the non-inverting output terminal of the third amplifier, respectively; a third capacitor, coupled between the non-inverting input terminal and the inverting output terminal of the first-loop amplifier; and a fourth capacitor, coupled between the inverting input terminal and the non-inverting output terminal of the first-loop amplifier.

9. The multipath instrumentation amplifier as described in claim 8, further comprising: The first automatic zeroing capacitor; A first switch, coupled to the first auto-zero capacitor, is connected to the inverting input terminal of the first loop amplifier or a second reference voltage; a second auto-zero capacitor; a second switch, coupled to the second auto-zero capacitor, is connected to the non-inverting input terminal of the first loop amplifier or the second reference voltage; a third loop amplifier, whose non-inverting input terminal is coupled to the first switch through the first auto-zero capacitor, and whose inverting input terminal is coupled to the second switch through the second auto-zero capacitor; a fourth loop amplifier; a third switch, coupled to the inverting output terminal of the third loop amplifier, is connected to the non-inverting input terminal of the fourth loop amplifier or the non-inverting input terminal of the third loop amplifier; a fourth switch, coupled to the non-inverting output terminal of the third loop amplifier, is connected to the inverting input terminal of the fourth loop amplifier or the inverting input terminal of the third loop amplifier; a fifth capacitor, coupled between the inverting output terminal and the non-inverting input terminal of the fourth loop amplifier; A sixth capacitor is coupled between the non-inverting output terminal and the inverting input terminal of the fourth circuit amplifier; and a fifth circuit amplifier is coupled between its non-inverting input terminal and its inverting input terminal and the inverting output terminal and the non-inverting output terminal of the fourth circuit amplifier, respectively, and the inverting output terminal and the non-inverting output terminal of the fifth circuit amplifier are coupled between the non-inverting input terminal and the inverting input terminal of the second circuit amplifier, respectively.

10. The multipath instrumentation amplifier as described in claim 8, further comprising: The first automatic zeroing capacitor; A first switch, coupled to the first auto-zero capacitor, is connected to the inverting input terminal of the first loop amplifier or a second reference voltage; a second auto-zero capacitor; a second switch, coupled to the second auto-zero capacitor, is connected to the non-inverting input terminal of the first loop amplifier or the second reference voltage; a third loop amplifier, the non-inverting input terminal of which is coupled to the first switch through the first auto-zero capacitor, and the inverting input terminal of which is coupled to the second switch through the second auto-zero capacitor; a fourth loop amplifier, the inverting output terminal and the non-inverting output terminal of which are respectively coupled to the inverting input terminal and the non-inverting input terminal of the second loop amplifier; a third switch, coupled to the inverting output terminal of the third loop amplifier, is connected to the non-inverting input terminal of the fourth loop amplifier or the non-inverting input terminal of the third loop amplifier; A fourth switch is coupled from the non-inverting output of the third loop amplifier to the inverting input of the fourth loop amplifier or the inverting input of the third loop amplifier; and a fifth capacitor is coupled between the inverting input and the non-inverting input of the fourth loop amplifier.

11. The multipath instrumentation amplifier as described in claim 8, further comprising: A third-loop amplifier, wherein its inverting input is coupled to the node between the first capacitor and the first-loop cutter, and its non-inverting input is coupled to the node between the second capacitor and the first-loop cutter; a second-loop cutter and a fourth-loop amplifier, wherein the non-inverting and inverting inputs of the fourth-loop amplifier are respectively coupled to the inverting and non-inverting outputs of the third-loop amplifier through the second-loop cutter; a fifth capacitor, coupled between the inverting and non-inverting inputs of the fourth-loop amplifier; a sixth capacitor, coupled between the non-inverting and inverting inputs of the fourth-loop amplifier; and a fifth-loop amplifier, wherein its non-inverting and inverting inputs are respectively coupled to the inverting and non-inverting outputs of the fourth-loop amplifier, and the inverting and non-inverting outputs of the fifth-loop amplifier are respectively coupled to the non-inverting and inverting inputs of the second-loop amplifier.

12. The multipath instrumentation amplifier as described in claim 8, further comprising: A first nested cutoff; And a second nested cutout, one end of the third capacitor is coupled to the non-inverting input terminal of the first loop amplifier through the first nested cutout, the other end of the third capacitor is coupled to the inverting output terminal of the first loop amplifier through the second nested cutout, one end of the fourth capacitor is coupled to the inverting input terminal of the first loop amplifier through the first nested cutout, and the other end of the fourth capacitor is coupled to the non-inverting output terminal of the first loop amplifier through the second nested cutout.

13. The multipath instrumentation amplifier as described in claim 2, further comprising: A first capacitor and a second capacitor; A first buffer, the inverting input and the non-inverting input of which are respectively coupled to the inverting input and the non-inverting input of the fifth amplifier through the first capacitor and the second capacitor, respectively; a first loop cutter, the input of which is respectively coupled to the non-inverting output and the inverting output of the first buffer; a second buffer, the inverting input and the non-inverting input of which are respectively coupled to the output of the first loop cutter; a third capacitor, coupled between the non-inverting output and the inverting output of the second buffer; and a loop amplifier, the non-inverting input and the inverting input of which are respectively coupled to the non-inverting output and the inverting output of the second buffer, and the non-inverting output and the inverting output of the loop amplifier are respectively coupled to the non-inverting output and the inverting output of the third amplifier.

14. The multipath instrumentation amplifier as claimed in claim 8 further includes a buffer, the inverting input and the non-inverting input of which are respectively coupled to the first capacitor and the second capacitor, and the non-inverting output and the inverting output of the buffer are respectively coupled to the input of the first loop cutter.

15. The multipath instrumentation amplifier as claimed in claim 2 further includes a fourth cutoff, the input of which is coupled to the non-inverting input and the inverting input of the third amplifier, respectively, and the output of the fourth cutoff is coupled to the non-inverting input and the inverting input of the first amplifier, respectively.

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