Transconductance amplifier and filter
By designing input, feedback, and common-mode feedback modules, the problem of insufficient linearity in transconductance amplifiers was solved, achieving high linearity and signal purity in transconductance capacitor filters.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- ORIGIN QUANTUM COMPUTING TECH (HEFEI) CO LTD
- Filing Date
- 2025-01-22
- Publication Date
- 2026-07-31
AI Technical Summary
The limited linearity of transconductance amplifiers restricts the linearity of transconductance capacitor filters.
By employing an input module, a feedback module, and a common-mode feedback module, the linearity of the transconductance amplifier is improved through source-level feedback active resistors and common-mode feedback signal adjustment.
It effectively suppresses the nonlinearity of the transconductance amplifier, maintains the stability of the operating point, and improves the linearity and signal purity of the transconductance capacitor filter.
Smart Images
Figure CN122495987A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of integrated circuit technology, specifically a transconductance amplifier and filter. Background Technology
[0002] High linearity filters can reduce nonlinear distortion and improve the separation of signal and noise during signal processing, resulting in a purer signal and maintaining its high quality and accuracy. Simultaneously, high linearity filters can also improve system performance, including increasing the dynamic range, reducing the bit error rate, and improving the signal-to-noise ratio.
[0003] As the only active module constituting a transconductance capacitive filter, the limited linear range of the transconductance amplifier greatly restricts the linearity of the transconductance capacitive filter.
[0004] Therefore, how to improve the linearity of transconductance amplifiers has become a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention
[0005] The purpose of this invention is to provide a transconductance amplifier and filter to overcome the shortcomings of the prior art, which can improve the linearity of the transconductance amplifier and filter.
[0006] The solution presented in this application is implemented through the following steps.
[0007] In a first aspect, the present application provides an example of a transconductance amplifier, which includes a first bias module that outputs a first bias current, a second bias module that outputs a second bias current, an input module composed of a first input transistor, a second input transistor, a third input transistor and a fourth input transistor, a feedback module composed of a first feedback transistor, a second feedback transistor, a third feedback transistor and a fourth feedback transistor, and a common-mode feedback module.
[0008] The sources of the first input transistor and the second input transistor are connected to the output terminal of the first bias module. The sources of the first feedback transistor and the drains of the second feedback transistor are connected to the sources of the first input transistor. The drains of the first feedback transistor and the sources of the second feedback transistor are connected to the sources of the second input transistor. The sources of the third input transistor and the fourth input transistor are connected to the output terminal of the second bias module. The sources of the third feedback transistor and the fourth feedback transistor are connected to the sources of the third input transistor. The drains of the third feedback transistor and the sources of the fourth feedback transistor are connected to the sources of the third input transistor.
[0009] The gates of the first input transistor, the fourth input transistor, the second feedback transistor, and the fourth feedback transistor are connected to the positive input terminal; the gates of the second input transistor, the third input transistor, the first feedback transistor, and the third feedback transistor are connected to the negative input terminal; the drains of the first input transistor and the third input transistor are connected to the negative output terminal; and the drains of the second input transistor and the fourth input transistor are connected to the positive output terminal.
[0010] The common-mode feedback module is connected to the positive-phase output terminal and the negative-phase output terminal respectively, and is used to stabilize the common-mode voltage of the transconductance amplifier output signal.
[0011] According to some examples of this application, the first bias module includes a first bias tube and a second bias tube of the same size;
[0012] The gates of the first bias transistor and the second bias transistor receive a first control signal, and the sources of the first bias transistor and the second bias transistor are grounded.
[0013] The drain of the first bias transistor is connected to the source of the first input transistor, and the drain of the second bias transistor is connected to the source of the second input transistor.
[0014] According to some examples of this application, the second bias module includes a third bias tube and a fourth bias tube of the same size;
[0015] The gates of the third bias transistor and the fourth bias transistor receive a second control signal, and the sources of the third bias transistor and the fourth bias transistor are grounded.
[0016] The drain of the third bias transistor is connected to the source of the third input transistor, and the drain of the fourth bias transistor is connected to the source of the fourth input transistor.
[0017] According to some examples of this application, the magnitude of the first bias current is equal to eight times the magnitude of the second bias current.
[0018] According to some examples of this application, the common-mode feedback module includes a common-mode feedback component and a first control transistor and a second control transistor;
[0019] The common-mode feedback component is used to generate a common-mode feedback signal based on the positive output signal at the positive output terminal and the negative output signal at the negative output terminal.
[0020] The first control transistor and the second control transistor are used to stabilize the common-mode voltage of the positive-phase output signal and the negative-phase output signal according to the common-mode feedback signal. The source of the first control transistor and the second control transistor are connected to the power supply voltage, and the gate of the first control transistor and the second control transistor are connected to the common-mode feedback component to receive the common-mode feedback signal. The drain of the first control transistor is connected to the negative-phase output terminal, and the drain of the second control transistor is connected to the positive-phase output terminal.
[0021] According to some examples of this application, the first control transistor and the second control transistor are PMOS transistors.
[0022] According to some examples of this application, the common-mode feedback component includes:
[0023] The third bias module is used to provide the target bias current;
[0024] The detection module, connected to the third bias module, is used to generate the common-mode feedback signal based on the positive-phase output signal and the negative-phase output signal.
[0025] According to some examples of this application, the third bias module includes a fifth bias tube and a sixth bias tube of the same size;
[0026] The gates of the fifth bias transistor and the sixth bias transistor receive a third control signal, and the sources of the fifth bias transistor and the sixth bias transistor are grounded.
[0027] The drain of the fifth bias transistor and the drain of the sixth bias transistor generate the target bias current;
[0028] The detection module includes a first detection tube, a second detection tube, a third detection tube, a fourth detection tube, a fifth detection tube, and a sixth detection tube;
[0029] The gate of the third detection tube receives the positive output signal, the gate of the sixth detection tube receives the negative output signal, and the gates of the fourth and fifth detection tubes receive a reference signal.
[0030] The sources of the third and fourth detection tubes are connected to the drain of the fifth bias tube, and the sources of the fifth and sixth detection tubes are connected to the drain of the sixth bias tube.
[0031] The sources of the first and second detection tubes are connected to the power supply voltage, and the drains of the fourth and fifth detection tubes are connected to the drain of the first detection tube. The common-mode feedback signal is output from the drain of the first detection tube.
[0032] The drain of the third detection tube is connected to the drain of the sixth detection tube, the drain of the sixth detection tube is connected to the drain of the second detection tube, the gate of the first detection tube is connected to the gate of the second detection tube, and the gate of the first detection tube is connected to the drain of the third detection tube.
[0033] Secondly, examples of this application present a filter comprising a predetermined number of transconductance amplifiers as described in the first aspect above.
[0034] According to some examples of this application, the filter includes a first-order filtering module and a second-order filtering module;
[0035] The first-order filtering module has two transconductance amplifiers, which are used to receive a positive-phase input signal and output a first positive-phase output signal, and to receive a negative-phase input signal and output a first negative-phase output signal.
[0036] The second-order filtering module has two transconductance amplifiers, which are used to receive the first positive-phase output signal and output the target positive-phase output signal, and to receive the first negative-phase output signal and output the target negative-phase output signal.
[0037] In the transconductance amplifier described in the foregoing example of this application, the transconductance amplifier includes a first bias module that outputs a first bias current, a second bias module that outputs a second bias current, an input module composed of a first input transistor, a second input transistor, a third input transistor, and a fourth input transistor, a feedback module composed of a first feedback transistor, a second feedback transistor, a third feedback transistor, and a fourth feedback transistor, and a common-mode feedback module. The first feedback transistor, the second feedback transistor, the third feedback transistor, and the fourth feedback transistor are two pairs of MOSFETs that serve as source-level feedback active resistors. These transistors can effectively suppress nonlinearity in the transconductance amplifier, and the common-mode feedback module can dynamically adjust the common-mode voltage of the transconductance amplifier's output signal, thereby keeping the transconductance amplifier's operating point in an optimal state, reducing nonlinear distortion caused by output signal voltage fluctuations, and improving linearity. Attached Figure Description
[0038] To illustrate this more clearly, the accompanying drawings used in the description will be briefly introduced below.
[0039] Figure 1 This is a structural diagram of a transconductance amplifier in one example of this application;
[0040] Figure 2 Here is a structural diagram of a common-mode feedback component in one example of this application;
[0041] Figure 3 This is a structural diagram of a filter in one example of this application. Detailed Implementation
[0042] To enable those skilled in the art to better understand the technical solutions in this application, the technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative effort should fall within the scope of protection of this application. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this application, and should not be construed as limiting this application.
[0043] In the description of this invention, it should be understood that the terms "center", "upper", "lower", "left", "right", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.
[0044] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.
[0045] High linearity filters can reduce nonlinear distortion and improve the separation of signal and noise during signal processing, resulting in a purer signal and maintaining high quality and accuracy. However, the limited linear range of the transconductance amplifier, the only active module in a transconductance capacitive filter, significantly restricts the linearity of the filter.
[0046] Based on this, such as Figure 1 As shown, one embodiment of the present invention provides a transconductance amplifier.
[0047] For example, the transconductance amplifier includes a first bias module 110 that outputs a first bias current, a second bias module 120 that outputs a second bias current, an input module 130 composed of a first input transistor M1, a second input transistor M2, a third input transistor M3 and a fourth input transistor M4, a feedback module 140 composed of a first feedback transistor M7, a second feedback transistor M8, a third feedback transistor M9 and a fourth feedback transistor M10, and a common-mode feedback module 150.
[0048] The source of the first input transistor M1 and the source of the second input transistor M2 are connected to the output terminal of the first bias module 110. The source of the first feedback transistor M7 and the drain of the second feedback transistor M8 are connected to the source of the first input transistor M1. The drain of the first feedback transistor M7 and the source of the second feedback transistor M8 are connected to the source of the second input transistor M2. The source of the third input transistor M3 and the source of the fourth input transistor M4 are connected to the output terminal of the second bias module 120. The source of the third feedback transistor M9 and the drain of the fourth feedback transistor M10 are connected to the source of the third input transistor M3. The drain of the third feedback transistor M9 and the source of the fourth feedback transistor M10 are connected to the source of the third input transistor M3.
[0049] The gates of the first input transistor M1, the fourth input transistor M4, the second feedback transistor M8, and the fourth feedback transistor M10 are connected to the positive input terminal. The gates of the second input transistor M2, the third input transistor M3, the first feedback transistor M7, and the third feedback transistor M9 are connected to the negative input terminal. The drains of the first input transistor M1 and the third input transistor M3 are connected to the negative output terminal. The drains of the second input transistor M2 and the fourth input transistor M4 are connected to the positive output terminal.
[0050] The common-mode feedback module 150 is connected to the positive and negative output terminals respectively to stabilize the common-mode voltage of the transconductance amplifier output signal.
[0051] In this configuration, the first input transistor M1, the second input transistor M2, the third input transistor M3, the fourth input transistor M4, the first feedback transistor M7, the second feedback transistor M8, the third feedback transistor M9, and the fourth feedback transistor M10 are all NMOS transistors. The first input transistor M1 and the second input transistor M2 have the same dimensions, the third input transistor M3 and the fourth input transistor M4 have the same dimensions, the first feedback transistor M7 and the second feedback transistor M8 have the same dimensions, and the third feedback transistor M9 and the fourth feedback transistor M10 have the same dimensions. The first input transistor M1 and the second input transistor M2, and the third input transistor M3 and the fourth input transistor M4 serve as two pairs of matched input transistors. The gates of the two pairs of input transistors are respectively connected to the positive input signal VIP and the negative input signal VIN, providing the same voltage to the gates of the two pairs of MOS transistors (the first feedback transistor M7 and the second feedback transistor M8, and the third feedback transistor M9 and the fourth feedback transistor M10) which serve as source-level feedback active resistors.
[0052] The transconductance amplifier provided in this application is used to convert the received differential voltage signal (positive input voltage signal VIP, negative input voltage signal VIN) into a differential current signal (negative output current signal Ion, positive output current signal Iop). In the transconductance amplifier, the first feedback transistor M7, the second feedback transistor M8, the third feedback transistor M9, and the fourth feedback transistor M10 are two pairs of MOS transistors that serve as source-level feedback active resistors. They can effectively suppress the nonlinearity in the transconductance amplifier, and the common-mode voltage of the output signal of the transconductance amplifier can be dynamically adjusted through the common-mode feedback module 150, thereby keeping the operating point of the transconductance amplifier in the optimal state, reducing nonlinear distortion caused by output signal voltage fluctuations, and improving linearity.
[0053] In one embodiment of this application, the first bias module 110 includes a first bias tube Mb1 and a second bias tube Mb2 of the same size;
[0054] The gate of the first bias transistor Mb1 and the gate of the second bias transistor Mb2 receive the first control signal, and the source of the first bias transistor Mb1 and the source of the second bias transistor Mb2 are grounded.
[0055] The drain of the first bias transistor Mb1 is connected to the source of the first input transistor M1, and the drain of the second bias transistor Mb2 is connected to the source of the second input transistor M2.
[0056] In this configuration, the first bias transistor Mb1 is connected in series with the first input transistor M1 to provide a stable first bias current for the first input transistor M1, and the second bias transistor Mb2 is connected in series with the second input transistor M2 to provide a stable first bias current for the second input transistor M2.
[0057] In one embodiment of this application, the second bias module 120 includes a third bias tube Mb3 and a fourth bias tube Mb4 of the same size;
[0058] The gates of the third bias transistor Mb3 and the fourth bias transistor Mb4 receive the second control signal, and the sources of the third bias transistor Mb3 and the fourth bias transistor Mb4 are grounded.
[0059] The drain of the third bias transistor Mb3 is connected to the source of the third input transistor M3, and the drain of the fourth bias transistor Mb4 is connected to the source of the fourth input transistor M4.
[0060] The third bias transistor Mb3 is connected in series with the third input transistor M3 to provide a stable second bias current for the third input transistor M3, and the fourth bias transistor Mb4 is connected in series with the fourth input transistor M4 to provide a stable second bias current for the fourth input transistor M4.
[0061] The first feedback transistor M7 and the second feedback transistor M8 form the first pair of source-level feedback MOSFETs, and the third feedback transistor M9 and the fourth feedback transistor M10 form the second pair of source-level feedback MOSFETs. Assuming the resistance of the first pair of source-level feedback MOSFETs is R1 and the resistance of the second pair is R2, and the differential input voltage of the transconductance amplifier is Vd (Vd = VIP - VIN), then the output current of the transconductance amplifier is:
[0062]
[0063] Wherein, the output current Io = Iop - Ion, Vdsat1 is the first control signal received by the first bias transistor Mb1 and the second bias transistor Mb2, that is, the overdrive saturation voltage of the first bias transistor Mb1 and the second bias transistor Mb2, Vdsat2 is the second control signal received by the third bias transistor Mb3 and the fourth bias transistor Mb4, that is, the overdrive saturation voltage of the third bias transistor Mb3 and the fourth bias transistor Mb4, Id1 is the first bias current, that is, the drain current of the first bias transistor Mb1 and the second bias transistor Mb2, Id2 is the second bias current, that is, the drain current of the third bias transistor Mb3 and the fourth bias transistor Mb4, and K is the conductivity factor.
[0064] Due to transconductance Therefore, according to the Taylor expansion formula, it can be written as:
[0065]
[0066] The change is as follows, taking into account the mobility degradation effect under strong field conditions:
[0067]
[0068] If the third-order nonlinear distortion term satisfies:
[0069]
[0070] Right now
[0071]
[0072] The transconductance in the transconductance amplifier can then be simplified to:
[0073]
[0074] Therefore, the magnitude of the first bias current provided by the first bias transistor Mb1 and the second bias transistor Mb2 in the transconductance amplifier must be a cube multiple of the magnitude of the second bias current provided by the third bias transistor Mb3 and the fourth bias transistor Mb4.
[0075] Based on this, in one embodiment of this application, the magnitude of the first bias current is equal to eight times the magnitude of the second bias current.
[0076] Specifically, the voltage magnitudes of the first control signal and the second control signal can be set to be equal, and the size of the first bias transistor Mb1 and the second bias transistor Mb2 can be set to be eight times the size of the third bias transistor Mb3 and the fourth bias transistor Mb4. This allows the first bias current provided by the first bias transistor Mb1 and the second bias transistor Mb2 in the transconductance amplifier to be eight times the second bias current provided by the third bias transistor Mb3 and the fourth bias transistor Mb4.
[0077] In one embodiment of this application, the common-mode feedback module 150 includes a common-mode feedback component ( Figure 1 The common-mode feedback component is not shown; only the common-mode feedback signal (CMFB) output by the common-mode feedback component and the first control transistor M5 and the second control transistor M6 are shown.
[0078] The common-mode feedback component is used to generate a common-mode feedback signal based on the positive output signal at the positive output terminal and the negative output signal at the negative output terminal.
[0079] The first control transistor M5 and the second control transistor M6 are used to stabilize the common-mode voltage of the positive and negative output signals according to the common-mode feedback signal. The sources of the first control transistor M5 and the second control transistor M6 are connected to the power supply voltage, and the gates of the first control transistor M5 and the second control transistor M6 are connected to the common-mode feedback component to receive the common-mode feedback signal. The drain of the first control transistor M5 is connected to the negative output terminal, and the drain of the second control transistor M6 is connected to the positive output terminal.
[0080] Specifically, the first control transistor M5 and the second control transistor M6 are PMOS transistors. The first control transistor M5 and the second control transistor M6 are connected through a common-mode feedback signal CMFB to stabilize the common-mode voltage of the positive-phase output voltage signal (VON) and the negative-phase output voltage signal (VOP).
[0081] like Figure 2 As shown, in one embodiment of this application, the common-mode feedback component includes:
[0082] The third bias module 210 is used to provide the target bias current;
[0083] The detection module 220, connected to the third bias module 210, is used to generate a common-mode feedback signal based on the positive and negative output signals.
[0084] Specifically, the third bias module 210 receives the third control signal and provides the target bias current to the detection module 220. The detection module 220 receives the target bias current and generates a common-mode feedback signal based on the positive phase output (voltage) signal (VOP) and negative phase output (voltage) signal (VON) of the transconductance amplifier.
[0085] In one embodiment of this application, the third bias module 210 includes a fifth bias tube M7 and a sixth bias tube M8 of the same size;
[0086] The gates of the fifth bias transistor M7 and the sixth bias transistor M8 receive the third control signal, and the sources of the fifth bias transistor M7 and the sixth bias transistor M8 are grounded.
[0087] The drain of the fifth bias transistor M7 and the drain of the sixth bias transistor M8 generate the target bias current;
[0088] The detection module 220 includes a first detection tube M1, a second detection tube M2, a third detection tube M3, a fourth detection tube M4, a fifth detection tube M5, and a sixth detection tube M6;
[0089] The gate of the third detection tube M3 receives a positive output signal, the gate of the sixth detection tube M6 receives a negative output signal, and the gates of the fourth detection tube M4 and the fifth detection tube M5 receive a reference signal.
[0090] The source of the third detection tube M3 and the source of the fourth detection tube M4 are connected to the drain of the fifth bias tube M7, and the source of the fifth detection tube M5 and the source of the sixth detection tube M6 are connected to the drain of the sixth bias tube M8.
[0091] The source of the first detection tube M1 and the source of the second detection tube M2 are connected to the power supply voltage. The drain of the fourth detection tube M4 and the drain of the fifth detection tube M5 are connected to the drain of the first detection tube M1. The drain of the first detection tube M1 outputs a common-mode feedback signal.
[0092] The drain of the third detection tube M3 is connected to the drain of the sixth detection tube M6, the drain of the sixth detection tube M6 is connected to the drain of the second detection tube M2, the gate of the first detection tube M1 is connected to the gate of the second detection tube M2, and the gate of the first detection tube M1 is connected to the drain of the third detection tube M3.
[0093] Among them, the fifth bias transistor M7 and the sixth bias transistor M8 are PMOS transistors, and the first detection transistor M1, the second detection transistor M2, the third detection transistor M3, the fourth detection transistor M4, the fifth detection transistor M5 and the sixth detection transistor M6 are NMOS transistors. The first detection transistor M1 and the second detection transistor M2 have the same size, and the third detection transistor M3, the fourth detection transistor M4, the fifth detection transistor M5 and the sixth detection transistor M6 have the same size.
[0094] Specifically, the gates of the fifth bias transistor M7 and the sixth bias transistor M8 are connected to the third control voltage to provide a stable target bias current. The third detection transistor M3 and the fourth detection transistor M4, and the fifth detection transistor M5 and the sixth detection transistor M6 are two pairs of differential input transistors. The gates of the fourth detection transistor M4 and the fifth detection transistor M5 are connected to the reference voltage VREF. The third detection transistor M3 and the sixth detection transistor M6 are connected to the output of the main circuit (i.e., the transconductance amplifier) to detect the magnitude of the differential output voltage signals (VON, VOP). The bias currents provided by the fifth bias transistor M7 and the sixth bias transistor M8 are equal; therefore, the currents flowing through the third detection transistor M3, the fourth detection transistor M4, the fifth detection transistor M5, and the sixth detection transistor M6 are equal. The first detection transistor M1 and the second detection transistor M2 are connected to the power supply voltage through their source stages, and the gates of the first detection transistor M1 and the second detection transistor M2 are connected to the drain of the second detection transistor M2 to achieve self-biasing. The drain of the first detection transistor M1 is connected to the drains of the fourth detection transistor M4 and the fifth detection transistor M5, and a common-mode feedback voltage signal CMFB is generated. The output common-mode voltage of the main circuit (i.e., the transconductance amplifier) is adjusted by the voltage of this common-mode feedback voltage signal.
[0095] Based on the same inventive concept, embodiments of the present invention also propose a filter, which includes a predetermined number of the above-mentioned transconductance amplifiers.
[0096] like Figure 3 As shown, in one embodiment of this application, the filter includes a first-order filter module 310 and a second-order filter module 320;
[0097] The first-order filter module 310 has two transconductance amplifiers. The two transconductance amplifiers are used to receive a positive input signal and output a first positive output signal, and to receive a negative input signal and output a first negative output signal.
[0098] The second-order filter module 320 has two transconductance amplifiers. The two transconductance amplifiers are used to receive the first positive phase output signal and output the target positive phase output signal, and to receive the first negative phase output signal and output the target negative phase output signal.
[0099] The first-order filter module 310 consists of a first OTA circuit (OTA1) and a second OTA circuit (OTA2), while the second-order filter module 320 consists of a third OTA circuit (OTA3) and a fourth OTA circuit (OTA4). OTA1, OTA2, OTA3, and OTA4 are transconductance amplifiers with the same structure as described above.
[0100] The first filtering module is used to receive differential input signals (Vinp, Vinn) and output a first differential output signal (Vop1, Von1). Specifically, the first filtering module receives the positive input signal (Vinp) through OTA1 and outputs the first positive output signal (Vop1), and receives the negative input signal (Vinn) through OTA2 and outputs the first negative output signal (Von1).
[0101] The second filtering module is used to receive the first differential output signal (Vop1, Von1) and output the target differential output signal (Vop, Von). Specifically, the second filtering module receives the first positive phase output signal (Vop1) through OTA3 and outputs the target positive phase output signal (Vop), and receives the first negative phase output signal (Von1) through OTA4 and outputs the target negative phase output signal (Von).
[0102] Specifically, such as Figure 3 As shown, the non-inverting input terminal of OTA1 receives the non-inverting input signal Vinp;
[0103] The negative input terminal of OTA1 is connected to the negative input terminal of OTA3, the positive output terminal of OTA4, the positive output terminal of OTA3, and the first terminal of the third capacitor C3.
[0104] The non-inverting output terminal of OTA1 outputs the first non-inverting output signal Vop1, and is connected to the first terminal of the first capacitor C1, the non-inverting input terminal of OTA3, and the non-inverting output terminal of OTA2. The non-inverting input terminal of OTA3 is used to receive the first non-inverting output signal Vop1.
[0105] The negative output terminal of OTA1 is connected to the first terminal of the second capacitor C1, the negative output terminal of OTA2, and the negative input terminal of OTA4;
[0106] The positive input terminal of OTA2 is connected to the positive input terminal of OTA4, the negative output terminal of OTA4, and the negative output terminal of OTA3, and is also connected to the first terminal of the fourth capacitor C4.
[0107] The negative phase input terminal of OTA2 receives the negative phase input signal;
[0108] The second terminals of the first, second, third, and fourth capacitors are grounded.
[0109] Furthermore, the filter also includes a first common-mode feedback component and a second common-mode feedback component, both of which employ... Figure 2The structure is shown. Specifically, the first common-mode feedback component generates a first common-mode feedback signal CMFB1 based on the first differential output signal (Vop1, Von1) and outputs it to OTA1 and OTA2. The second common-mode feedback component generates a second common-mode feedback signal CMFB2 based on the target differential output signal (Vop, Von) and outputs it to OTA3 and OTA4.
[0110] For the first-order filter module 310 composed of OTA1 and OTA2, its differential output voltage V1d (V1d=Vop1-Von1) can be derived as follows:
[0111]
[0112] Where I1 and I2 are the output currents of OTA1 and OTA2, gm1 is the transconductance of the transconductance units OTA1 and OTA2, and Vid is the differential input voltage of the second-order low-pass filter (Vid = Vinp - Vinn).
[0113] Similarly, the differential output voltage Vod (Vod = Vop - Von) of the second-order filter module 320 is:
[0114]
[0115] Where I3 and I4 are the output currents of OTA3 and OTA4, and gm2 is the transconductance of the transconductance units OTA3 and OTA4.
[0116] Therefore, the transfer function of the filter is:
[0117]
[0118] As can be seen, all signals in this structure are differential signals. Each OTA receives signals with similar assignments and phases at its positive and negative input terminals, resulting in a reduced input voltage swing and alleviating the need for high swing and linearity.
[0119] In summary, the filter provided in this application includes four transconductance amplifiers, two common-mode feedback components, and four capacitors. The transconductance amplifiers convert the input voltage signal into a current signal, amplifying only the current, resulting in good high-frequency characteristics. This allows the constructed filter to operate in a higher frequency range. Furthermore, the fully differential structure, with two pairs of source-level feedback MOSFETs added as resistors, expands the circuit's linear range and suppresses linearity. The common-mode feedback components detect the output signal of the transconductance amplifiers and adjust the filter's output using the generated common-mode feedback signal, ensuring stable common-mode output.
[0120] In the description of this specification, references to terms such as "some embodiments" or "example" indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments. In addition, those skilled in the art can combine and integrate the different embodiments or examples described in this specification.
[0121] The above are merely preferred embodiments of the present invention and do not constitute any limitation on the present invention. Any equivalent substitutions or modifications made by those skilled in the art to the technical solutions and content disclosed in the present invention without departing from the scope of the present invention shall be deemed to have remained within the protection scope of the present invention.
Claims
1. A transconductance amplifier, characterized in that, The transconductance amplifier includes a first bias module that outputs a first bias current, a second bias module that outputs a second bias current, an input module consisting of a first input transistor, a second input transistor, a third input transistor, and a fourth input transistor, a feedback module consisting of a first feedback transistor, a second feedback transistor, a third feedback transistor, and a fourth feedback transistor, and a common-mode feedback module. The sources of the first input transistor and the second input transistor are connected to the output terminal of the first bias module. The sources of the first feedback transistor and the drains of the second feedback transistor are connected to the sources of the first input transistor. The drains of the first feedback transistor and the sources of the second feedback transistor are connected to the sources of the second input transistor. The sources of the third input transistor and the fourth input transistor are connected to the output terminal of the second bias module. The sources of the third feedback transistor and the fourth feedback transistor are connected to the sources of the third input transistor. The drains of the third feedback transistor and the sources of the fourth feedback transistor are connected to the sources of the third input transistor. The gates of the first input transistor, the fourth input transistor, the second feedback transistor, and the fourth feedback transistor are connected to the positive input terminal; the gates of the second input transistor, the third input transistor, the first feedback transistor, and the third feedback transistor are connected to the negative input terminal; the drains of the first input transistor and the third input transistor are connected to the negative output terminal; and the drains of the second input transistor and the fourth input transistor are connected to the positive output terminal. The common-mode feedback module is connected to the positive-phase output terminal and the negative-phase output terminal respectively, and is used to stabilize the common-mode voltage of the transconductance amplifier output signal.
2. The transconductance amplifier according to claim 1, characterized in that, The first bias module includes a first bias tube and a second bias tube of the same size; The gates of the first bias transistor and the second bias transistor receive a first control signal, and the sources of the first bias transistor and the second bias transistor are grounded. The drain of the first bias transistor is connected to the source of the first input transistor, and the drain of the second bias transistor is connected to the source of the second input transistor.
3. The transconductance amplifier according to claim 1, characterized in that, The second bias module includes a third bias tube and a fourth bias tube of the same size; The gates of the third bias transistor and the fourth bias transistor receive the second control signal, and the sources of the third bias transistor and the fourth bias transistor are grounded. The drain of the third bias transistor is connected to the source of the third input transistor, and the drain of the fourth bias transistor is connected to the source of the fourth input transistor.
4. The transconductance amplifier according to claim 1, characterized in that, The magnitude of the first bias current is eight times that of the second bias current.
5. The transconductance amplifier according to claim 1, characterized in that, The common-mode feedback module includes a common-mode feedback component and a first control transistor and a second control transistor; The common-mode feedback component is used to generate a common-mode feedback signal based on the positive output signal at the positive output terminal and the negative output signal at the negative output terminal. The first control transistor and the second control transistor are used to stabilize the common-mode voltage of the positive-phase output signal and the negative-phase output signal according to the common-mode feedback signal. The source of the first control transistor and the second control transistor are connected to the power supply voltage, and the gate of the first control transistor and the second control transistor are connected to the common-mode feedback component to receive the common-mode feedback signal. The drain of the first control transistor is connected to the negative-phase output terminal, and the drain of the second control transistor is connected to the positive-phase output terminal.
6. The transconductance amplifier according to claim 5, characterized in that, The first control transistor and the second control transistor are PMOS transistors.
7. The transconductance amplifier according to claim 5, characterized in that, The common-mode feedback component includes: The third bias module is used to provide the target bias current; The detection module, connected to the third bias module, is used to generate the common-mode feedback signal based on the positive-phase output signal and the negative-phase output signal.
8. The transconductance amplifier according to claim 7, characterized in that, The third bias module includes a fifth bias tube and a sixth bias tube of the same size; The gates of the fifth bias transistor and the sixth bias transistor receive a third control signal, and the sources of the fifth bias transistor and the sixth bias transistor are grounded. The drain of the fifth bias transistor and the drain of the sixth bias transistor generate the target bias current; The detection module includes a first detection tube, a second detection tube, a third detection tube, a fourth detection tube, a fifth detection tube, and a sixth detection tube; The gate of the third detection tube receives the positive output signal, the gate of the sixth detection tube receives the negative output signal, and the gates of the fourth and fifth detection tubes receive a reference signal. The sources of the third and fourth detection tubes are connected to the drain of the fifth bias tube, and the sources of the fifth and sixth detection tubes are connected to the drain of the sixth bias tube. The sources of the first and second detection tubes are connected to the power supply voltage, and the drains of the fourth and fifth detection tubes are connected to the drain of the first detection tube. The common-mode feedback signal is output from the drain of the first detection tube. The drain of the third detection tube is connected to the drain of the sixth detection tube, the drain of the sixth detection tube is connected to the drain of the second detection tube, the gate of the first detection tube is connected to the gate of the second detection tube, and the gate of the first detection tube is connected to the drain of the third detection tube.
9. A filter, characterized in that, The filter includes a predetermined number of transconductance amplifiers as described in any one of claims 1 to 8.
10. The filter according to claim 9, characterized in that, The filter includes a first-order filtering module and a second-order filtering module; The first-order filtering module has two transconductance amplifiers, which are used to receive a positive-phase input signal and output a first positive-phase output signal, and to receive a negative-phase input signal and output a first negative-phase output signal. The second-order filtering module has two transconductance amplifiers, which are used to receive the first positive-phase output signal and output the target positive-phase output signal. Used to receive the first negative phase output signal and output the target negative phase output signal.