Transconductance operational amplifier for analog front end of sensor
阅读说明：本技术 一种用于传感器模拟前端的跨导运算放大器 (Transconductance operational amplifier for analog front end of sensor ) 是由 朱樟明 王凌 刘术彬 王静宇 刘帘曦 于 2020-06-16 设计创作，主要内容包括：本发明涉及一种用于传感器模拟前端的跨导运算放大器,其特征在于,包括：依次连接的浮地电压源模块、输入分流模块和负载电流镜输出模块,其中,浮地电压源模块为翻转电压跟随器结构；输入分流模块根据输入的差分电压信号产生小信号电流,并将小信号电流进行分流,其中较大比例的电流导入接地端,较小比例的电流输入至负载电流镜输出模块；负载电流镜输出模块根据输入的较小比例的电流产生相应的镜像输出电流。本发明的跨导运算放大器,通过输入分流模块和负载电流镜输出模块将输入差分管的等效跨导减小至原来的<Image he="150" wi="233" file="DDA0002541812110000011.GIF" imgContent="drawing" imgFormat="GIF" orientation="portrait" inline="no"></Image>在合适的直流偏置下,当N和M取到足够大时,放大器的跨导值的数量级可以降低到nS级,而且在实现低跨导的同时具有高的线性度。(The invention relates to a transconductance operational amplifier for an analog front end of a sensor, which is characterized by comprising the following components: the load current mirror output module is connected with the input shunt module and the input shunt module in sequence, wherein the floating ground voltage source module is of an overturning voltage follower structure; the input shunt module generates small-signal current according to the input differential voltage signal and shunts the small-signal current, wherein the current with a larger proportion is led into a grounding terminal, and the current with a smaller proportion is input into the load current mirror output module; the load current mirror output module generates corresponding mirror output current according to the input current with smaller proportion. The transconductance operational amplifier reduces the equivalent transconductance of the input differential tube to the original value through the input shunt module and the load current mirror output module When N and M are sufficiently large, under appropriate dc bias, the transconductance of the amplifier can be reduced to nS level,and has high linearity while achieving low transconductance.)
1. A transconductance operational amplifier for an analog front end of a sensor, comprising: a floating ground voltage source module (1), an input shunt module (2) and a load current mirror output module (3) which are connected in sequence, wherein,
the floating ground voltage source module (1) is of an overturning voltage follower structure and is used for providing a constant voltage difference between an input tube grid and a pair tube source electrode of the input shunt module (2);
the input shunt module (2) generates a small signal current according to the input differential voltage signal and shunts the small signal current, wherein a larger proportion of the current is led into a ground terminal, and a smaller proportion of the current is input into the load current mirror output module (3);
the load current mirror output module (3) generates corresponding mirror output current according to the input current with smaller proportion;
wherein the current of smaller proportion is the current of small signalThe mirror output current being the small signal current
2. The transconductance operational amplifier for a sensor analog front end according to claim 1, characterized in that the input tube gates of the input shunt module (2) and their pair tube sources are cross-coupled by the floating voltage source module (1).
3. The transconductance operational amplifier for a sensor analog front end according to claim 1, characterized in that said floating ground voltage source module (1) comprises: a first MOS transistor (M1), a second MOS transistor (M2), a third MOS transistor (M3), a fourth MOS transistor (M4) and a current source (I)B) Wherein, in the step (A),
the first MOS transistor (M1) and the second MOS transistor (M2) are both PMOS transistors, and the third MOS transistor (M3) and the fourth MOS transistor (M4) are both NMOS transistors;
the source electrode of the first MOS transistor (M1) and the source electrode of the second MOS transistor (M2) are both connected with an Analog Voltage (AVDD);
the drain electrode of the first MOS transistor (M1) is connected with the source electrode of the third MOS transistor (M3), and the gate electrode of the first MOS transistor is connected with the drain electrode of the third MOS transistor (M3);
the drain electrode of the second MOS transistor (M2) is connected with the source electrode of the fourth MOS transistor (M4), and the gate electrode of the second MOS transistor is connected with the drain electrode of the fourth MOS transistor (M4);
the drains of the third MOS transistor (M3) and the fourth MOS transistor (M4) are both connected with the current source (I)B) The first terminal of (1), the current source (I)B) Is connected to ground (AGND);
the drain electrode of the first MOS tube (M1), the drain electrode of the second MOS tube (M2), the gate electrode of the third MOS tube (M3) and the gate electrode of the fourth MOS tube (M4) are used as differential voltage signal output ends of the floating ground voltage source module (1).
4. The operational transconductance amplifier for a sensor analog front end according to claim 3, characterized in that the input shunt module (2) comprises a fifth MOS transistor (M5), a sixth MOS transistor (M6), a seventh MOS transistor (M7) and an eighth MOS transistor (M8), wherein,
the fifth MOS transistor (M5), the sixth MOS transistor (M6), the seventh MOS transistor (M7) and the eighth MOS transistor (M8) are all PMOS transistors, and the ratio of the width-to-length ratio of the fifth MOS transistor (M5) to the sixth MOS transistor (M6) and the ratio of the width-to-length ratio of the eighth MOS transistor (M8) to the seventh MOS transistor (M7) are both M;
the source electrode of the fifth MOS transistor (M5) and the source electrode of the sixth MOS transistor (M6) are both connected with the drain electrode of the first MOS transistor (M1), and the gate electrode of the fifth MOS transistor (M5) and the gate electrode of the sixth MOS transistor (M6) are both connected with the gate electrode of the fourth MOS transistor (M4);
the source electrode of the seventh MOS transistor (M7) and the source electrode of the eighth MOS transistor (M8) are both connected with the drain electrode of the second MOS transistor (M2), and the gate electrode of the seventh MOS transistor (M7) and the gate electrode of the eighth MOS transistor (M8) are both connected with the gate electrode of the third MOS transistor (M3);
the drains of the fifth MOS transistor (M5) and the eighth MOS transistor (M8) are both connected to the ground terminal (AGND);
the drains of the sixth MOS transistor (M6) and the seventh MOS transistor (M7) are used as a small proportion current output end of the input shunt module (2).
5. The operational transconductance amplifier for a sensor analog front end according to claim 4, characterized in that the load current mirror output module (3) comprises a ninth MOS transistor (M9), a tenth MOS transistor (M10), an eleventh MOS transistor (M11), a twelfth MOS transistor (M12), a thirteenth MOS transistor (M13) and a fourteenth MOS transistor (M14), wherein,
the ninth MOS transistor (M9), the tenth MOS transistor (M10), the eleventh MOS transistor (M11) and the twelfth MOS transistor (M12) are NMOS transistors, and the thirteenth MOS transistor (M13) and the fourteenth MOS transistor (M14) are PMOS transistors;
the ratio of the width-to-length ratio of the tenth MOS transistor (M10) to the ninth MOS transistor (M9) and the ratio of the width-to-length ratio of the eleventh MOS transistor (M11) to the twelfth MOS transistor (M12) are both N;
the sources of the ninth MOS transistor (M9), the tenth MOS transistor (M10), the eleventh MOS transistor (M11) and the twelfth MOS transistor (M12) are all connected to the ground terminal (AGND);
the drain electrode of the ninth MOS transistor (M9) is connected with the drain electrode of the thirteenth MOS transistor (M13), and the gate electrode of the ninth MOS transistor is connected with the gate electrode of the tenth MOS transistor (M10);
the drain electrode of the tenth MOS tube (M10) is respectively connected with the gate electrode thereof and the drain electrode of the sixth MOS tube (M6);
the drain electrode of the eleventh MOS transistor (M11) is respectively connected with the gate electrode thereof and the drain electrode of the seventh MOS transistor (M7);
the drain electrode of the twelfth MOS tube (M12) is connected with the drain electrode of the fourteenth MOS tube (M14), and the gate electrode of the twelfth MOS tube (M12) is connected with the gate electrode of the eleventh MOS tube (M11);
the sources of the thirteenth MOS transistor (M13) and the fourteenth MOS transistor (M14) are both connected to the ground terminal (AGND), and the gates are both connected to the common mode feedback voltage (CMFB).
Technical Field
The invention belongs to the technical field of design of an analog front end of a sensor, and particularly relates to a transconductance operational amplifier for the analog front end of the sensor.
Background
Currently, the integrated circuit used in the medical field receives more and more attention and research, and wearable devices capable of monitoring physiological signals in real time are one of the most potential development directions. The front-end processing circuit of the sensor determines the quality of the acquired signal and the final monitoring result to some extent. The use of a filter for removing interference signals other than the target signal is an important loop in the analog front-end circuit.
In common physiological signals, the frequency of a photoplethysmographic pulse wave signal is 0.6-16 Hz, the frequency of respiration is 0.1-10 Hz, the frequency of an electrocardiosignal is about 0.01-250 Hz, and the frequency of a heart sound signal is 5-2 kHz. It can be seen that the physiological signal frequency is in the low frequency range. Conventional filters require larger passive components (primarily resistors and capacitors) to achieve lower cut-off frequencies, which can be costly to implement in an integrated circuit.
At present, various schemes are tried to realize a fully integrated low-cut-off frequency filter, and the application of a Gm-C filter to medium and high frequencies is mature, but for processing low-frequency physiological signals, although some research results exist, a stable amplifier structure and a mature design method are lacked, and further exploration is still needed. For a Gm-C filter, the key part determining its cut-off frequency is Gm/C, where Gm is the equivalent transconductance value of the amplifier.
Therefore, it is necessary to provide a Gm-C filter with very low transconductance and high linearity to achieve a low cut-off frequency.
Disclosure of Invention
In order to solve the above problems in the prior art, the present invention provides a transconductance operational amplifier for an analog front end of a sensor. The technical problem to be solved by the invention is realized by the following technical scheme:
the invention provides a transconductance operational amplifier for an analog front end of a sensor, which comprises: the floating ground voltage source module, the input shunt module and the load current mirror output module are connected in sequence, wherein,
the floating ground voltage source module is of an overturning voltage follower structure and is used for providing a constant voltage difference between an input tube grid and a pair tube source electrode of the input shunt module;
the input shunt module generates a small signal current according to an input differential voltage signal and shunts the small signal current, wherein a larger proportion of the current is led into a ground terminal, and a smaller proportion of the current is input to the load current mirror output module;
the load current mirror output module generates corresponding mirror image output current according to the input current with smaller proportion;
wherein the current of smaller proportion is the current of small signal
In one embodiment of the invention, the input tube grid and the pair tube source of the input shunt module are cross-coupled through the floating ground voltage source module.
In one embodiment of the present invention, the floating voltage source module includes: a first MOS transistor, a second MOS transistor, a third MOS transistor, a fourth MOS transistor and a current source,
the first MOS tube and the second MOS tube are both PMOS tubes, and the third MOS tube and the fourth MOS tube are both NMOS tubes;
the source electrode of the first MOS tube and the source electrode of the second MOS tube are both connected with analog voltage;
the drain electrode of the first MOS tube is connected with the source electrode of the third MOS tube, and the grid electrode of the first MOS tube is connected with the drain electrode of the third MOS tube;
the drain electrode of the second MOS tube is connected with the source electrode of the fourth MOS tube, and the grid electrode of the second MOS tube is connected with the drain electrode of the fourth MOS tube;
the drain electrodes of the third MOS tube and the fourth MOS tube are both connected with the first end of the current source, and the second end of the current source is connected with the grounding end;
and the drain electrode of the first MOS tube, the drain electrode of the second MOS tube, the grid electrode of the third MOS tube and the grid electrode of the fourth MOS tube are used as differential voltage signal output ends of the floating ground voltage source module.
In one embodiment of the present invention, the input shunting module includes a fifth MOS transistor, a sixth MOS transistor, a seventh MOS transistor, and an eighth MOS transistor, wherein,
the fifth MOS transistor, the sixth MOS transistor, the seventh MOS transistor and the eighth MOS transistor are all PMOS transistors, and the ratio of the width-to-length ratio of the fifth MOS transistor to the sixth MOS transistor and the ratio of the width-to-length ratio of the eighth MOS transistor to the seventh MOS transistor are all M;
the source electrode of the fifth MOS tube and the source electrode of the sixth MOS tube are both connected with the drain electrode of the first MOS tube, and the grid electrode of the fifth MOS tube and the grid electrode of the sixth MOS tube are both connected with the grid electrode of the fourth MOS tube;
the source electrode of the seventh MOS tube and the source electrode of the eighth MOS tube are both connected with the drain electrode of the second MOS tube, and the grid electrode of the seventh MOS tube and the grid electrode of the eighth MOS tube are both connected with the grid electrode of the third MOS tube;
the drain electrodes of the fifth MOS tube and the eighth MOS tube are both connected with the grounding terminal;
and the drain electrodes of the sixth MOS tube and the seventh MOS tube are used as the current output ends of the input shunt module with smaller proportion.
In one embodiment of the present invention, the load current mirror output module includes a ninth MOS transistor, a tenth MOS transistor, an eleventh MOS transistor, a twelfth MOS transistor, a thirteenth MOS transistor and a fourteenth MOS transistor, wherein,
the ninth MOS transistor, the tenth MOS transistor, the eleventh MOS transistor and the twelfth MOS transistor are NMOS transistors, and the thirteenth MOS transistor and the fourteenth MOS transistor are PMOS transistors;
the ratio of the width to the length of the tenth MOS transistor to the width to the length of the ninth MOS transistor and the ratio of the width to the length of the eleventh MOS transistor to the width to the length of the twelfth MOS transistor are both N;
the source electrodes of the ninth MOS transistor, the tenth MOS transistor, the eleventh MOS transistor and the twelfth MOS transistor are all connected with the grounding terminal;
the drain electrode of the ninth MOS tube is connected with the drain electrode of the thirteenth MOS tube, and the grid electrode of the ninth MOS tube is connected with the grid electrode of the tenth MOS tube;
the drain electrode of the tenth MOS tube is respectively connected with the grid electrode of the tenth MOS tube and the drain electrode of the sixth MOS tube;
the drain electrode of the eleventh MOS tube is respectively connected with the grid electrode of the eleventh MOS tube and the drain electrode of the seventh MOS tube;
the drain electrode of the twelfth MOS tube is connected with the drain electrode of the fourteenth MOS tube, and the grid electrode of the twelfth MOS tube is connected with the grid electrode of the eleventh MOS tube;
and the source electrodes of the thirteenth MOS tube and the fourteenth MOS tube are both connected with the grounding end, and the grid electrodes are both connected with common-mode feedback voltage.
Compared with the prior art, the invention has the beneficial effects that:
1. according to the transconductance operational amplifier for the analog front end of the sensor, the input tube grid of the input shunt module and the pair tube source electrode thereof are in cross coupling through the floating ground voltage source module, compared with a traditional source coupling differential pair, the linearity of the transmission characteristic is greatly improved, and the linear input range is expanded;
2. the transconductance operational amplifier for the analog front end of the sensor reduces the equivalent transconductance of the input differential tube to the original value through the input shunt module and the load current mirror output moduleUnder proper DC bias, when N and M are large enough, the order of magnitude of transconductance value of the amplifier can be reduced to nS level, and the same effect of low transconductance is achievedHas high linearity.
The foregoing description is only an overview of the technical solutions of the present invention, and in order to make the technical means of the present invention more clearly understood, the present invention may be implemented in accordance with the content of the description, and in order to make the above and other objects, features, and advantages of the present invention more clearly understood, the following preferred embodiments are described in detail with reference to the accompanying drawings.
Drawings
Fig. 1 is a block diagram of a transconductance operational amplifier for an analog front end of a sensor according to an embodiment of the present invention;
FIG. 2 is a schematic structural diagram of a floating ground voltage source module according to an embodiment of the present invention;
fig. 3 is a schematic structural diagram of a transconductance operational amplifier for an analog front end of a sensor according to an embodiment of the present invention.
Detailed Description
To further illustrate the technical means and effects of the present invention adopted to achieve the predetermined objects, a transconductance operational amplifier for a sensor analog front end according to the present invention is described in detail below with reference to the accompanying drawings and the detailed description.
The foregoing and other technical matters, features and effects of the present invention will be apparent from the following detailed description of the embodiments, which is to be read in connection with the accompanying drawings. The technical means and effects of the present invention adopted to achieve the predetermined purpose can be more deeply and specifically understood through the description of the specific embodiments, however, the attached drawings are provided for reference and description only and are not used for limiting the technical scheme of the present invention.
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