Common-mode feedback circuit, control method, and operational amplifier

Abstract

The present invention discloses a common-mode feedback circuit, control method, and operational amplifier, relating to the field of circuit design technology. The common-mode feedback circuit includes: a common-mode sensing and error amplification subcircuit and a current summing subcircuit for providing a common-mode feedback voltage; the current summing subcircuit is coupled to the common-mode sensing and error amplification subcircuit; the common-mode sensing and error amplification subcircuit includes two sets of differential amplifier input transistors with opposite polarity, each set of differential amplifier input transistors including two pairs of transistors with the same polarity, one transistor in each pair of transistors being controlled by a differential output signal, and the other transistor being controlled by a common-mode signal. The control method described above applies to the common-mode feedback circuit. The operational amplifier described above includes the common-mode feedback circuit.

Description

Technical Field

[0001] The present invention relates to the technical field of circuit design, and in particular to a common-mode feedback circuit, a control method, and an operational amplifier. Background Art

[0002] With the development of circuit design technology, operational amplifiers (op amps), as a key branch of the field, have also experienced rapid growth. Fully differential op amps, due to their wide output dynamic range and ability to suppress common-mode noise and even-order harmonics, have gained widespread application. These amplifiers require a common-mode feedback circuit to stabilize the common-mode output voltage.

[0003] Currently, differential error amplifier common-mode feedback circuits are an alternative. These circuits require no resistive loads or additional clocks and can be used in continuous-time systems. These circuits typically use two differential transistor pairs to sense the common-mode voltage and compare it with the desired output common-mode voltage. However, to achieve sufficient common-mode feedback loop gain, current differential error amplifier common-mode feedback circuits require both differential transistor pairs and the tail current source in the feedback circuit to operate in the saturation region.

[0004] However, in order to make the two pairs of differential pairs and the tail current source in the feedback circuit operate in the saturation region, the output voltage of the operational amplifier should be greater than the sum of the gate-source voltage (VGS) of the input pair and the saturation drain-source voltage (VDSAT) of the tail current source. In the standard complementary metal oxide semiconductor (CMOS) process, this voltage sum is 1 volt, resulting in the feedback circuit limiting the output voltage swing of the operational amplifier, reducing the reliability and stability of the feedback circuit and the fully differential operational amplifier. Summary of the Invention

[0005] The object of the present invention is to provide a common-mode feedback circuit, a control method and an operational amplifier, which are used to solve the problem that the feedback circuit limits the output voltage swing of the operational amplifier, thereby reducing the reliability and stability of the feedback circuit and the fully differential operational amplifier.

[0006] In a first aspect, the present invention provides a common-mode feedback circuit for use with an operational amplifier. The common-mode feedback circuit includes: a common-mode sensing and error amplification subcircuit and a current summing subcircuit for providing a common-mode feedback voltage; the current summing subcircuit is coupled to the common-mode sensing and error amplification subcircuit; the common-mode sensing and error amplification subcircuit includes two groups of differential amplifier input transistors with opposite polarities, each group of differential amplifier input transistors includes two pairs of transistors with the same polarity, and one transistor in each pair of transistors is controlled by a differential output signal, and the other transistor is controlled by a common-mode signal.

[0007] When the differential output voltage is a first differential signal and the common-mode signal is a first common-mode signal, one group of the differential amplifier input pair transistors is in an on state, and the other group of the differential amplifier input pair transistors is in an off state; when the differential output voltage is a second differential signal and the common-mode signal is a first common-mode signal, both groups of the differential amplifier input pair transistors are in an on state;

[0008] Each group of the differential amplifier input pair tubes is used to provide a common-mode small-signal current to the current summing subcircuit under the control of the differential output voltage and the common-mode signal; the current summing subcircuit is used to determine a common-mode feedback voltage according to the common-mode small-signal current.

[0009] As can be seen from the above, the common-mode feedback circuit provided by the present invention can further determine the common-mode feedback voltage by alternately turning on two sets of differential amplifier input pairs with opposite polarity in different differential output voltage ranges (i.e., the input voltage range of the common-mode feedback circuit). Compared with the prior art, while maintaining the advantages of conventional circuits that do not require an additional clock and do not introduce a resistive load, it overcomes the disadvantage of conventional circuits that limit the output voltage swing, and can ensure the normal operation of the common-mode feedback circuit in scenarios with a wide output swing. Specifically, when two sets of differential amplifier input pairs with opposite polarity are alternately turned on in different differential output voltage ranges, a rail-to-rail input voltage range can be achieved, overcoming the prior art problem that the feedback circuit limits the output voltage swing of the operational amplifier because the output voltage of the operational amplifier must be greater than the sum of the input pair gate-source voltage (VGS) and the tail current source saturation drain-source voltage (VDSAT). It can be seen that the common-mode feedback circuit provided by the present invention can expand the application scenarios of the common-mode feedback circuit while maintaining the high transconductance gain and small chip area consumption of the differential error amplification common-mode feedback circuit. That is, the common-mode feedback circuit can be applied to more application scenarios, for example, it can be applied to low-power supply voltage operational amplifiers. Further, the stability and reliability of the common-mode feedback circuit can be improved.

[0010] In a second aspect, the present invention provides a common-mode feedback circuit control method, which is applied to the common-mode feedback circuit described in the first aspect, and the method includes:

[0011] When the differential output voltage is a first differential signal and the common-mode signal is a first common-mode signal, one group of the differential amplifier input pair transistors is in an on state, and the other group of the differential amplifier input pair transistors is in an off state; when the differential output voltage is a second differential signal and the common-mode signal is a first common-mode signal, both groups of the differential amplifier input pair transistors are in an on state;

[0012] After determining the states of the two groups of differential amplifier input tubes, determining a common mode voltage component based on the differential output voltage;

[0013] determining a common-mode small-signal current based on the common-mode voltage component and the common-mode signal;

[0014] A common-mode feedback voltage value is determined based on the common-mode small-signal current.

[0015] Compared with the prior art, while maintaining the advantages of the traditional circuit that no additional clock is required and no resistive load is introduced, the disadvantage of the traditional circuit that the output voltage swing is limited is overcome. The beneficial effects of the common-mode feedback circuit control method provided by the present invention are the same as the beneficial effects of the common-mode feedback circuit described in the first aspect above, and will not be repeated here.

[0016] In a third aspect, the present invention provides an operational amplifier comprising any common-mode feedback circuit described in the first aspect.

[0017] Compared with the prior art, while maintaining the advantages of the traditional circuit that no additional clock is required and no resistive load is introduced, the disadvantage of the traditional circuit that the output voltage swing is limited is overcome. The beneficial effects of the operational amplifier provided by the present invention are the same as the beneficial effects of the common-mode feedback circuit described in the first aspect above, and will not be repeated here. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The drawings described herein are used to provide a further understanding of the present invention and constitute a part of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0019] Figure 1 A schematic diagram of the circuit structure of a common-mode feedback circuit provided in an embodiment of the present application is shown;

[0020] Figure 2 A circuit diagram of a common-mode feedback circuit provided by an embodiment of the present application when one set of differential amplifier input pairs is in an on state is shown;

[0021] Figure 3A circuit diagram of another common-mode feedback circuit provided by an embodiment of the present application is shown when one set of differential amplifier input pairs is in an on state. DETAILED DESCRIPTION

[0022] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0023] It should be noted that when an element is referred to as being “fixed on” or “disposed on” another element, it may be directly on the other element or indirectly on the other element. When an element is referred to as being “connected to” another element, it may be directly connected to the other element or indirectly connected to the other element.

[0024] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be understood to indicate or imply relative importance or implicitly specify the number of the technical features indicated. Thus, a feature specified as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, "plurality" means two or more, unless otherwise specifically defined. "Several" means one or more, unless otherwise specifically defined.

[0025] In the description of the present invention, it should be understood that the terms "up", "down", "front", "back", "left", "right", etc., indicating directions or positional relationships, are based on the directions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as a limitation on the present invention.

[0026] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood in a broad sense. For example, they may refer to fixed, detachable, or integral connections; mechanical or electrical connections; direct or indirect connections through an intermediate medium; and may encompass internal communication between two components or interaction between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0027] Currently, in a differential error amplification common-mode feedback circuit, in order to ensure that both pairs of differential transistors and the tail current source in the feedback circuit operate in the saturation region, the output voltage of the operational amplifier should be greater than the sum of the gate-source voltage (VGS) of the input transistors and the saturation drain-source voltage (VDSAT) of the tail current source. In a standard complementary metal oxide semiconductor (CMOS) process, this voltage sum is 1 volt. As a result, the feedback circuit limits the output voltage swing of the operational amplifier, reducing the reliability and stability of the feedback circuit and the fully differential operational amplifier.

[0028] To address the above problems, an embodiment of the present invention provides a common-mode feedback circuit. Figure 1 The circuit structure diagram of the common mode feedback circuit provided by the embodiment of the present invention is illustrated. Figure 1 The common-mode feedback circuit provided in an embodiment of the present invention is applied to an operational amplifier. The common-mode feedback circuit includes a common-mode sensing and error amplification subcircuit 10 and a current summing subcircuit 20 for providing a common-mode feedback voltage. The current summing subcircuit 20 is coupled to the common-mode sensing and error amplification subcircuit 10. The common-mode sensing and error amplification subcircuit 10 includes two sets of differential amplifier input transistors 101 with opposite polarity. Each set of differential amplifier input transistors 101 includes two pairs of transistors 101A with the same polarity. In each pair of transistors 101A, one transistor 101a is controlled by a differential output signal (VOP / VON), and the other transistor 101b is controlled by a common-mode signal (VCM). The differential output signal (VOP / VON) serves as the input of the common-mode feedback circuit.

[0029] When the differential output voltage is a first differential signal and the common-mode signal is a first common-mode signal, one group of the differential amplifier input pair tubes 101 is in an on state, and the other group of the differential amplifier input pair tubes 101 is in an off state; when the differential output voltage is a second differential signal and the common-mode signal is a first common-mode signal, both groups of the differential amplifier input pair tubes 101 are in an on state.

[0030] Each group of the differential amplifier input pair transistors 101 is used to provide a common-mode small signal current to the current summing sub-circuit 20 under the control of the differential output voltage and the common-mode signal.

[0031] The current summing subcircuit 20 is configured to determine a common-mode feedback voltage according to the common-mode small-signal current.

[0032] In this application, the common-mode sensing and error amplification subcircuit 10 senses the output common-mode voltage, subtracts it from the desired common-mode voltage, and amplifies it to generate a corresponding common-mode error small-signal current. A larger small-signal current generated for the same difference indicates a greater common-mode feedback loop gain and better common-mode feedback.

[0033] As can be seen from the above, the common-mode feedback circuit provided by the present invention can be used to further determine the common-mode feedback voltage by alternately turning on two sets of differential amplifier input pairs with opposite polarity in different differential output voltage ranges (that is, the input voltage range of the common-mode feedback circuit). Compared with the prior art, while maintaining the advantages of the conventional circuit that does not require an additional clock and does not introduce a resistive load, it overcomes the disadvantage of the conventional circuit that limits the output voltage swing, and can ensure the normal use of the common-mode feedback circuit in scenarios with a wide output swing. When the two sets of differential amplifier input pairs with opposite polarity are alternately turned on in different differential output voltage ranges, a rail-to-rail input voltage range can be achieved, overcoming the prior art problem that the output voltage of the operational amplifier is limited by the feedback circuit because the output voltage of the operational amplifier must be greater than the sum of the gate-source voltage (VGS) of the input pair and the saturation drain-source voltage (VDSAT) of the tail current source. It can be seen that the common-mode feedback circuit provided by the present invention can expand the application scenarios of the common-mode feedback circuit while maintaining the high transconductance gain and small chip area consumption of the differential error amplification common-mode feedback circuit. That is, the common-mode feedback circuit can be applied to more application scenarios, for example, it can be applied to low-power supply voltage operational amplifiers. Further, the stability and reliability of the common-mode feedback circuit can be improved.

[0034] Reference Figure 1 The common-mode feedback circuit further includes: a common-source common-gate sub-circuit 30, which is coupled to the current summing sub-circuit 20 and the two groups of differential amplifier input pairs 101 respectively.

[0035] The cascode sub-circuit 30 includes: Figure 1 Shown are the 7th N-type transistor N7, the 8th N-type transistor N8, the 9th N-type transistor N9 and the 10th N-type transistor N10.

[0036] The function of the cascode sub-circuit 30 is to change the direction of the small signal current generated by the P-type input transistor pair group (composed of two pairs of P transistors) so that it is superimposed in the same direction with the small signal current generated by the N-type input transistor pair group (composed of two pairs of N transistors).

[0037] The cascode sub-circuit may be a folded cascode sub-circuit, and one of the small-signal currents generated by the complementary inputs may have its direction changed by the cascode sub-circuit, so that the currents in the small-signal summing sub-circuit are always superimposed simultaneously.

[0038] The two sets of differential amplifier input pairs can extract the common-mode voltage component (VOC) of the differential output of the operational amplifier and compare the common-mode voltage component with the common-mode signal (that is, the expected output common-mode voltage VCM) to determine the common-mode small signal current based on the common-mode voltage component and the common-mode signal.

[0039] Reference Figure 1 , wherein the transistors contained in one group of the differential amplifier input pair tubes are P-type transistors, and the transistors contained in the other group of the differential amplifier input pair tubes are N-type transistors.

[0040] The current summing subcircuit 20 includes: Figure 1 The seventh P-type transistor P7, the eighth P-type transistor P8, the ninth P-type transistor P9 and the tenth P-type transistor P10 shown in FIG. Figure 1 The third N-type transistor N3, the fourth N-type transistor N4, the fifth N-type transistor N5, the sixth N-type transistor N6 and the third P-type transistor P3, the fourth P-type transistor P4, the fifth P-type transistor P5, and the sixth P-type transistor P6 are shown.

[0041] The function of the current summing subcircuit 20 is to mirror the small-signal current generated by the transistors on one side of the input pair (including N and P polarities, located in two sets of transistors respectively) controlled by the differential output signal, and sum the currents at the P9 / N10 connection point, thereby obtaining twice the small-signal current at transistor P10 that generates the common-mode feedback voltage (VCMFB), that is, obtaining twice the common-mode feedback loop gain of the traditional structure.

[0042] The two sets of differential amplifier input pairs can extract the common-mode voltage component (VOC) of the operational amplifier's differential output and compare this common-mode voltage component with the common-mode signal (i.e., the desired output common-mode voltage VCM) to determine the common-mode small-signal current based on the common-mode voltage component and the common-mode signal. The current summing subcircuit is further configured to: mirror the common-mode small-signal current to obtain two sets of common-mode small-signal currents; sum the two sets of common-mode small-signal currents to obtain a target small-signal current; and determine the common-mode feedback voltage based on the target small-signal current. This means that, based on the target small-signal current, a common-mode feedback voltage (VCMFB) is generated to regulate the controlled current source in the operational amplifier. This implements common-mode closed-loop negative feedback, thereby clamping the output common-mode voltage of the operational amplifier to the common-mode signal (VCM).

[0043] Reference Figure 1The common-mode sensing and error amplification sub-circuit 10 further includes: a tail current source 102 coupled to each pair of the differential amplifier input pairs 101A in the two groups of opposite polarities.

[0044] Among them, the tail current source 102 is Figure 1 The first N-type transistor N1, the second N-type transistor N2, and the first P-type transistor P1 and the second P-type transistor P2 are shown. Specifically, P1 is a tail current source for P3 and P4, and provides bias current for P3 and P4. P2 is a tail current source for P5 and P6, and provides bias current for P5 and P6. N1 is a tail current source for N3 and N4, and provides bias current for N3 and N4. N2 is a tail current source for N5 and N6, and provides bias current for N5 and N6.

[0045] Optionally, when the voltage of the first differential signal is less than the first preset voltage threshold and the common-mode signal is the first common-mode signal, the differential amplifier input pair tube corresponding to the P-type transistor is in an on state, and the differential amplifier input tube corresponding to the N-type transistor is in an off state, wherein the first preset voltage threshold is the sum of the input pair tube gate-source voltage and the tail current source saturation drain-source voltage.

[0046] Figure 2 FIG1 shows a circuit diagram of a common-mode feedback circuit provided by an embodiment of the present application when a set of differential amplifier input pairs are in a conducting state, as shown in FIG1 . Figure 2 As shown, when the differential amplifier input pair corresponding to the P-type transistor is in the on state and the differential amplifier input pair corresponding to the N-type transistor is in the off state, P3, P4, P5, and P6 are in the on state, N3, N4, N5, and N6 are in the off state, P1 provides bias current for P3 and P4, and P2 provides bias current for P5 and P6, then P3, P4, P5, and P6 determine the common-mode voltage component (V OC); and determining a common-mode small-signal current based on the common-mode voltage component (VOC) and the common-mode signal (VCM); wherein one of the small-signal currents generated by the complementary input changes its direction through the common-source and common-gate sub-circuit (N7 / N8 / N9 / N10), so that the two small-signal currents in the small-signal summing sub-circuit (P7 / P8 / P9 / P10) can always be superimposed simultaneously, and the small-signal summing sub-circuit can determine a common-mode feedback voltage value based on the common-mode small-signal current.

[0047] Optionally, the voltage of the first differential signal is greater than a second preset voltage threshold, the common-mode signal is the first common-mode signal, the differential amplifier input pair corresponding to the P-type transistor is in an off state, and the differential amplifier input transistor corresponding to the N-type transistor is in an on state. The second preset voltage threshold is a voltage difference obtained by subtracting the gate-source voltage of the input pair from the power supply voltage and the saturated drain-source voltage of the tail current source from the saturated drain-source voltage of the tail current source.

[0048] In an optional embodiment provided in the embodiments of the present application, Figure 3 FIG. 4 shows another circuit diagram of a common-mode feedback circuit provided by an embodiment of the present application when one set of differential amplifier input pairs is in a conducting state. Figure 3 As shown in the figure: when the differential amplifier input pair tube corresponding to the N-type transistor is in the on state and the differential amplifier input tube corresponding to the P-type transistor is in the off state, P3, P4, P5, and P6 are in the off state, N3, N4, N5, and N6 are in the on state, N1 provides bias current for N3 and N4, and N2 provides bias current for N5 and N6, then N3, N4, N5, and N6 determine the common-mode voltage component (V OC); and determining a common-mode small-signal current based on the common-mode voltage component (VOC) and the common-mode signal (VCM); wherein one of the small-signal currents generated by the complementary input changes its direction through the common-source and common-gate sub-circuit (N7 / N8 / N9 / N10), so that the two small-signal currents in the small-signal summing sub-circuit (P7 / P8 / P9 / P10) can always be superimposed simultaneously, and the small-signal summing sub-circuit can determine a common-mode feedback voltage value based on the common-mode small-signal current.

[0049] Optionally, the voltage of the second differential signal is greater than the first preset voltage threshold and less than the second preset voltage threshold, and the common mode signal is the first common mode signal. In this case, see Figure 1, the differential amplifier input pair corresponding to the P-type transistor and the N-type transistor are all in the on state. P3, P4, P5, P6 and N3, N4, N5, N6 are all in the on state, N1 provides bias current for N3 and N4, N2 provides bias current for N5 and N6, P1 provides bias current for P3 and P4, and P2 provides bias current for P5 and P6, then P3, P4, P5, P6, N3, N4, N5, N6 determine the common mode voltage component (VOC) based on the differential output voltage (VOP / VON); and based on the common mode The voltage component (VOC) and the common-mode signal (VCM) determine a common-mode small-signal current; wherein, one of the small-signal currents generated by the complementary input changes its direction through the common-source and common-gate sub-circuit (N7 / N8 / N9 / N10), so that the two small-signal currents in the small-signal summation sub-circuit (P7 / P8 / P9 / P10) can always be superimposed simultaneously, and the small-signal summation sub-circuit can determine the common-mode feedback voltage value based on the common-mode small-signal current.

[0050] As can be seen from the above, the common-mode feedback circuit provided by the present invention can be used to further determine the common-mode feedback voltage by alternately turning on two sets of differential amplifier input pairs with opposite polarity in different differential output voltage ranges (that is, the input voltage range of the common-mode feedback circuit). Compared with the prior art, while maintaining the advantages of the conventional circuit that does not require an additional clock and does not introduce a resistive load, it overcomes the disadvantage of the conventional circuit that limits the output voltage swing, and can ensure the normal use of the common-mode feedback circuit in scenarios with a wide output swing. When the two sets of differential amplifier input pairs with opposite polarity are alternately turned on in different differential output voltage ranges, a rail-to-rail input voltage range can be achieved, overcoming the prior art problem that the output voltage of the operational amplifier is limited by the feedback circuit because the output voltage of the operational amplifier must be greater than the sum of the gate-source voltage (VGS) of the input pair and the saturation drain-source voltage (VDSAT) of the tail current source. It can be seen that the common-mode feedback circuit provided by the present invention can expand the application scenarios of the common-mode feedback circuit while maintaining the high transconductance gain and small chip area consumption of the differential error amplification common-mode feedback circuit. That is, the common-mode feedback circuit can be applied to more application scenarios, for example, it can be applied to low-power supply voltage operational amplifiers. Further, the stability and reliability of the common-mode feedback circuit can be improved.

[0051] An embodiment of the present invention further provides an operational amplifier comprising at least one of the above-mentioned common-mode feedback circuits.

[0052] Compared with the prior art, while maintaining the advantages of the traditional circuit that no additional clock is required and no resistive load is introduced, the disadvantage of the traditional circuit that the output voltage swing is limited is overcome. The beneficial effects of the operational amplifier provided by the present invention are the same as those of the above-mentioned common-mode feedback circuit, and will not be repeated here.

[0053] An embodiment of the present invention provides a common-mode feedback circuit control method, which is applied to the above-mentioned common-mode feedback circuit. The method includes:

[0054] When the differential output voltage is a first differential signal and the common-mode signal is a first common-mode signal, one group of the differential amplifier input pair transistors is in an on state, and the other group of the differential amplifier input pair transistors is in an off state; when the differential output voltage is a second differential signal and the common-mode signal is a first common-mode signal, both groups of the differential amplifier input pair transistors are in an on state;

[0055] After determining the states of the two groups of differential amplifier input tubes, determining a common mode voltage component based on the differential output voltage;

[0056] determining a common-mode small-signal current based on the common-mode voltage component and the common-mode signal;

[0057] A common-mode feedback voltage value is determined based on the common-mode small-signal current.

[0058] Compared with the prior art, while maintaining the advantages of the traditional circuit that no additional clock is required and no resistive load is introduced, the disadvantage of the traditional circuit that the output voltage swing is limited is overcome. The beneficial effects of the common-mode feedback circuit control method provided by the present invention are the same as the beneficial effects of the above-mentioned common-mode feedback circuit, and will not be repeated here.

[0059] Although alternative embodiments of the present invention have been described, those skilled in the art may make additional changes and modifications to these embodiments once they become aware of the basic creative concepts. Therefore, the appended claims are intended to be interpreted as including alternative embodiments and all changes and modifications that fall within the scope of the embodiments of the present invention.

[0060] Finally, it should be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity from another, and do not necessarily require or imply any actual relationship or order between these entities. Moreover, the terms "comprises," "includes," or any other variations thereof are intended to encompass non-exclusive inclusion, such that an article or terminal device comprising a series of elements includes not only those elements, but also other elements not explicitly listed, or elements inherent to such article or terminal device. In the absence of further limitations, an element defined by the phrase "comprising a..." does not exclude the presence of additional identical elements in the article or terminal device comprising the element.

[0061] The above are only specific embodiments of the present invention, but the scope of protection of the present invention is not limited to them. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present invention should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A common-mode feedback circuit, characterized in that: Applied to an operational amplifier, the common-mode feedback circuit includes: a common-mode sensing and error amplification subcircuit and a current summing subcircuit for providing a common-mode feedback voltage; the current summing subcircuit is coupled to the common-mode sensing and error amplification subcircuit; the common-mode sensing and error amplification subcircuit includes two groups of differential amplifier input pairs with opposite polarities, each group of differential amplifier input pairs includes two pairs of transistors with the same polarity, one transistor in each pair of transistors with the same polarity is controlled by a differential output signal, and the other transistor is controlled by a common-mode signal; When the differential output voltage is a first differential signal and the common-mode signal is a first common-mode signal, one group of the differential amplifier input pair transistors is in an on state, and the other group of the differential amplifier input pair transistors is in an off state; when the differential output voltage is a second differential signal and the common-mode signal is a first common-mode signal, both groups of the differential amplifier input pair transistors are in an on state; Each group of the differential amplifier input pair tubes is used to provide a common-mode small-signal current to the current summing subcircuit under the control of the differential output voltage and the common-mode signal; the current summing subcircuit is used to determine a common-mode feedback voltage according to the common-mode small-signal current.

2. The circuit according to claim 1, wherein: The transistors contained in one group of the differential amplifier input pair transistors are P-type transistors, and the transistors contained in the other group of the differential amplifier input pair transistors are N-type transistors.

3. The circuit according to claim 2, characterized in that The voltage of the first differential signal is less than a first preset voltage threshold, the differential amplifier input pair corresponding to the P-type transistor is in an on state, and the differential amplifier input pair corresponding to the N-type transistor is in an off state; Or, the voltage of the first differential signal is greater than a second preset voltage threshold, the differential amplifier input pair corresponding to the P-type transistor is in an off state, and the differential amplifier input pair corresponding to the N-type transistor is in an on state.

4. The circuit according to claim 3, characterized in that The voltage of the second differential signal is greater than a first preset voltage threshold and less than a second preset voltage threshold, and the differential amplifier input pair transistors corresponding to the P-type transistor and the N-type transistor are both in an on state.

5. The circuit according to claim 4, characterized in that The first preset voltage threshold is the sum of the input pair gate-source voltage and the tail current source saturation drain-source voltage; the second preset voltage threshold is the power supply voltage minus the input pair gate-source voltage minus the tail current source saturation drain-source voltage.

6. The circuit according to claim 1, wherein: The common-mode feedback circuit further includes: a cascode sub-circuit, wherein the cascode sub-circuit is coupled to the current summing sub-circuit and the two groups of differential amplifier input pairs respectively.

7. The circuit according to any one of claims 1 to 6, characterized in that: The common-mode sensing and error amplification sub-circuit further includes: a tail current source coupled to each pair of the two groups of the differential amplification input pairs of transistors with opposite polarities.

8. The circuit according to any one of claims 1 to 6, characterized in that: The current summing subcircuit is further configured to: perform mirror processing on the common-mode small-signal current to obtain two groups of common-mode small-signal currents; Summing the two groups of common-mode small-signal currents to obtain a target small-signal current; The common-mode feedback voltage is determined based on the target small-signal current.

9. A common-mode feedback circuit control method, characterized in that: Applied to the common-mode feedback circuit of claim 1, the method comprises: When the differential output voltage is a first differential signal and the common-mode signal is a first common-mode signal, one group of the differential amplifier input pair transistors is in an on state, and the other group of the differential amplifier input pair transistors is in an off state; when the differential output voltage is a second differential signal and the common-mode signal is a first common-mode signal, both groups of the differential amplifier input pair transistors are in an on state; After determining the states of the two groups of differential amplifier input tubes, determining a common mode voltage component based on the differential output voltage; determining a common-mode small-signal current based on the common-mode voltage component and the common-mode signal; A common-mode feedback voltage value is determined based on the common-mode small-signal current.

10. An operational amplifier, characterized in that: The common-mode feedback circuit comprises the common-mode feedback circuit according to any one of claims 1 to 8.

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