Operational amplification circuit

Abstract

The embodiment of the invention discloses an operational amplifier circuit. The operational amplifier circuit comprises an operational amplifier, a first parallel reverse diode module, a second parallel reverse diode module, a first capacitor module, a second capacitor module, a first resistor module and a second resistor module; the positive input end of the operational amplifier inputs first voltage, the positive input end of the operational amplifier is electrically connected with the first end of the first parallel backward diode module, the second end of the first parallel backward diode module is electrically connected with the first end of the first resistor module, and bias voltage is connected to the second end of the first resistor module. The third end of the first resistor module is electrically connected with the negative output end of the operational amplifier, and the positive input end of the operational amplifier is electrically connected with the first end of the first capacitor module; a common-mode voltage is input into the common-mode input end of the operational amplifier. According to the operational amplifier circuit provided by the embodiment of the invention, input and output common-mode voltages can be separated, and the common-mode rejection ratio can be improved.

Description

TECHNICAL FIELD

[0001] The embodiment of the present application relates to communication technology, in particular to an operational amplifier circuit. BACKGROUND

[0002] With the development of the Internet of Things and machines, human-computer interaction is more and more frequent, and the requirement for signal transmission accuracy is also higher and higher. In order to adapt to the processing of various signals, the operational amplifier in the operational amplifier circuit needs to be adjusted by the program to make the conversion range signal of the analog-to-digital converter uniform, so as to improve the measurement accuracy. At present, the existing operational amplifier circuit has the problem that the common-mode voltage of input and output cannot be separated, which affects the common-mode gain and reduces the common-mode rejection ratio. SUMMARY

[0003] The embodiment of the present application provides an operational amplifier circuit to separate the common-mode voltage of input and output and improve the common-mode rejection ratio.

[0004] The embodiment of the present application provides an operational amplifier circuit, which comprises an operational amplifier, a first parallel reverse diode module, a second parallel reverse diode module, a first capacitor module, a second capacitor module, a first resistor module and a second resistor module.

[0005] The positive input end of the operational amplifier inputs a first voltage, the positive input end of the operational amplifier is electrically connected with the first end of the first parallel reverse diode module, the second end of the first parallel reverse diode module is electrically connected with the first end of the first resistor module, the second end of the first resistor module is connected with a bias voltage, the third end of the first resistor module is electrically connected with the negative output end of the operational amplifier, the positive input end of the operational amplifier is electrically connected with the first end of the first capacitor module, and the second end of the first capacitor module is electrically connected with the negative output end of the operational amplifier.

[0006] The negative input end of the operational amplifier inputs a second voltage, the negative input end of the operational amplifier is grounded through a capacitor, the negative input end of the operational amplifier is electrically connected with the first end of the second parallel reverse diode module, the second end of the second parallel reverse diode module is electrically connected with the first end of the second resistor module, the second end of the second resistor module is connected with the bias voltage, the third end of the second resistor module is electrically connected with the positive output end of the operational amplifier, the negative input end of the operational amplifier is electrically connected with the first end of the second capacitor module, and the second end of the second capacitor module is electrically connected with the positive output end of the operational amplifier; and the common-mode input end of the operational amplifier inputs a common-mode voltage.

[0007] Optionally, the first parallel reverse diode module comprises a first switch tube and a second switch tube, a first pole of the first switch tube and a first pole of the second switch tube serve as a first end of the first parallel reverse diode module, a gate of the first switch tube is electrically connected with the first pole of the first switch tube, a second pole of the first switch tube and a second pole of the second switch tube serve as a second end of the first parallel reverse diode module, and a gate of the second switch tube is electrically connected with the second pole of the second switch tube.

[0008] Optionally, the second parallel reverse diode module comprises a third switch tube and a fourth switch tube, a first pole of the third switch tube and a first pole of the fourth switch tube serve as a first end of the second parallel reverse diode module, a gate of the third switch tube is electrically connected with the first pole of the third switch tube, a second pole of the third switch tube and a second pole of the fourth switch tube serve as a second end of the second parallel reverse diode module, and a gate of the fourth switch tube is electrically connected with the second pole of the fourth switch tube.

[0009] Optionally, the first resistance module comprises a first resistance and a second resistance, a first end of the first resistance serves as a first end of the first resistance module, a second end of the first resistance serves as a second end of the first resistance module, the first end of the first resistance is electrically connected with a first end of the second resistance, and a second end of the second resistance serves as a third end of the first resistance module.

[0010] Optionally, a voltage at the first end of the first resistance R1 and a voltage at the first end of the second resistance R2 are both (Vbias-Vcm)×R2 / (R1+R2)+Vcm, Vbias is the bias voltage, and Vcm is the common-mode voltage.

[0011] Optionally, the second resistance module comprises a third resistance and a fourth resistance, a first end of the third resistance serves as a first end of the second resistance module, a second end of the third resistance serves as a second end of the second resistance module, the first end of the third resistance is electrically connected with a first end of the fourth resistance, and a second end of the fourth resistance serves as a third end of the second resistance module.

[0012] Optionally, the first capacitance module and the second capacitance module each comprise a plurality of parallel branches, each of the branches comprises a capacitance and a switch connected in series.

[0013] Optionally, the operational amplifier circuit further comprises two input capacitances, a positive input end of the operational amplifier inputs the first voltage through one of the input capacitances, and a negative input end of the operational amplifier inputs the second voltage through the other input capacitance.

[0014] Optionally, the first resistance module has the same resistance as the second resistance module.

[0015] Optionally, the common-mode voltage is half of the power voltage of the operational amplifier.

[0016] The operational amplifier circuit provided by the embodiment of the present application comprises an operational amplifier, a first parallel reverse diode module, a second parallel reverse diode module, a first capacitor module, a second capacitor module, a first resistance module and a second resistance module. The positive input end of the operational amplifier is input with a first voltage. The positive input end of the operational amplifier is electrically connected with the first end of the first parallel reverse diode module. The second end of the first parallel reverse diode module is electrically connected with the first end of the first resistance module. The second end of the first resistance module is connected with a bias voltage. The third end of the first resistance module is electrically connected with the negative output end of the operational amplifier. The positive input end of the operational amplifier is electrically connected with the first end of the first capacitor module. The second end of the first capacitor module is electrically connected with the negative output end of the operational amplifier. The negative input end of the operational amplifier is input with a second voltage. The negative input end of the operational amplifier is grounded through a capacitor. The negative input end of the operational amplifier is electrically connected with the first end of the second parallel reverse diode module. The second end of the second parallel reverse diode module is electrically connected with the first end of the second resistance module. The second end of the second resistance module is connected with a bias voltage. The third end of the second resistance module is electrically connected with the positive output end of the operational amplifier. The negative input end of the operational amplifier is electrically connected with the first end of the second capacitor module. The second end of the second capacitor module is electrically connected with the positive output end of the operational amplifier. The common-mode input end of the operational amplifier is input with a common-mode voltage. The operational amplifier circuit provided by the embodiment of the present application provides a direct current path for the positive input end of the operational amplifier through the first resistance module and the first parallel reverse diode module, provides a direct current path for the negative input end of the operational amplifier through the second resistance module and the second parallel reverse diode module, so as to ensure the reliability of the direct current path, and separates the common-mode voltage of the input and the output through the bias voltage, the first resistance module and the second resistance module, so as to improve the common-mode rejection ratio. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 is a structural schematic diagram of an operational amplifier circuit in the prior art;

[0018] Figure 2 is a structural schematic diagram of another operational amplifier circuit in the prior art;

[0019] Figure 3 is a structural schematic diagram of an operational amplifier circuit provided by the embodiment of the present application. DETAILED DESCRIPTION

[0020] The application will be described in further detail below with reference to the drawings and embodiments. It is to be understood that the specific embodiments described herein are merely illustrative of the application and are not to be used to limit the scope of the application. It is also to be understood that, for the purpose of the present description, some of the elements in the drawings are not shown to scale.

[0021] Figure 1 is a structural schematic diagram of an operational amplifier circuit in the prior art, Figure 2 is a structural schematic diagram of another operational amplifier circuit in the prior art. Referring to Figure 1 and Figure 2 The main feedback mode of the operational amplifier AMP in the prior art operational amplifier circuit is resistance array feedback and capacitance array feedback. As shown in Figure 1 , the gain Gain of the operational amplifier is selected by the ratio of the resistance value Rf of the feedback resistance and the resistance value Ri of the input resistance, i.e. Gain=-Rf / Ri. The resistance array feedback mode will increase the noise and reduce the signal-to-noise ratio, and deteriorate the performance of the entire circuit, because the input resistance and the feedback resistance will generate thermal noise, which will finally act on the output terminal of the operational amplifier and enter the entire signal path. As shown in Figure 2 , the capacitance array feedback. For the capacitor working in the AC coupling state, the capacitor itself will not generate noise contribution, and the capacitor Cf (connected with the switch SW, the resistance R and the capacitor Ci, Figure 1 and Figure 2The input signal of the operational amplifier AMP in the circuit is input through ports VI1, VI2 and VI3, and the output signal is output through ports VO1 and VO2) to realize a low-noise programmable gain operational amplifier in a feedback mode, but since the capacitor feedback array has no direct current passage, the common mode level cannot be determined, and the operational amplifier cannot work normally. In order to enable the operational amplifier with capacitor feedback to work normally, a direct current passage needs to be added to the feedback capacitor, and a resistor is usually used to complete the direct current passage. However, due to the existence of resistor thermal noise, noise interference is still increased. Therefore, in order to reduce the influence of resistor noise in the direct current passage, a large resistor (such as greater than 100G) is usually used to make the feedback resistor R close to an open circuit state. However, the large resistor will occupy most of the area, which is not practical in actual application. In the prior art, two opposite diodes are used to establish a direct current passage. However, due to the non-linear influence of the diode impedance, different signal amplitudes will have different performance, which is not stable. When a resistor or a diode is used to establish a direct current passage, the output and the input have the same common mode level. Since the input end of the operational amplifier uses different architectures, different requirements are required for the input voltage. For example: the power supply voltage is 1.5V, in order to obtain a larger output swing, the common mode voltage is usually 0.75V. In order to reduce the leakage voltage of the input pair transistor at the input end of the operational amplifier, a high-voltage device is usually used as the input pair transistor, which requires a minimum input voltage. 0.75V cannot meet the normal working requirements. If a depletion mode input pair transistor is used, due to the low output resistance, the common mode gain will be affected, and the common mode rejection ratio will be reduced.

[0022] Based on this, the embodiment provides an operational amplification circuit. Figure 3 It is a structural schematic diagram of an operational amplification circuit provided by the embodiment of the application, referring to Figure 3 The operational amplification circuit comprises an operational amplifier AMP, a first parallel reverse diode module 11, a second parallel reverse diode module 12, a first capacitor module 21, a second capacitor module 22, a first resistor module 31 and a second resistor module 32.

[0023] The positive input end of the operational amplifier AMP inputs a first voltage VIP, the positive input end of the operational amplifier AMP is electrically connected with the first end of the first parallel reverse diode module 11, the second end of the first parallel reverse diode module 11 is electrically connected with the first end of the first resistance module 31, the second end of the first resistance module 31 is connected with a bias voltage Vbias, the third end of the first resistance module 31 is electrically connected with the negative output end of the operational amplifier AMP, the positive input end of the operational amplifier AMP is electrically connected with the first end of the first capacitor module 21, and the second end of the first capacitor module 21 is electrically connected with the negative output end of the operational amplifier AMP; the negative input end of the operational amplifier AMP inputs a second voltage VIN, the negative input end of the operational amplifier AMP is grounded through a capacitor, the negative input end of the operational amplifier AMP is electrically connected with the first end of the second parallel reverse diode module 12, the second end of the second parallel reverse diode module 12 is electrically connected with the first end of the second resistance module, the second end of the second resistance module 32 is connected with the bias voltage Vbias, the third end of the second resistance module 32 is electrically connected with the positive output end of the operational amplifier AMP, the negative input end of the operational amplifier AMP is electrically connected with the first end of the second capacitor module 22, and the second end of the second capacitor module 22 is electrically connected with the positive output end of the operational amplifier AMP; and the common-mode input end of the operational amplifier AMP inputs a common-mode voltage Vcm.

[0024] Specifically, the positive input terminal of the operational amplifier AMP inputs the first voltage VIP, and the negative input terminal of the operational amplifier AMP inputs the second voltage VIN. Since the negative input terminal of the operational amplifier AMP is grounded, the second voltage VIN is 0 V, serving as a pseudo differential input. The common-mode voltage of the positive output terminal (output voltage VOP) and the negative output terminal (output voltage VON) of the operational amplifier AMP is controlled by the common-mode voltage Vcm inputted by the common-mode input terminal of the operational amplifier AMP. The gain of the operational amplifier AMP is related to the capacitance value of the first capacitor module 21 and the capacitance value of the second capacitor module 22. The capacitance value of the first capacitor module 21 and the capacitance value of the second capacitor module 22 are adjustable. By adjusting the capacitance value of the first capacitor module 21 and the capacitance value of the second capacitor module 22, the gain of the operational amplifier AMP is changed. The bias voltage Vbias is inputted to the second end of the first resistor module 31, and the direct current voltage Vp (the direct current voltage Vp serving as the common-mode input voltage) at the first end of the first resistor module 31 is transmitted to the positive input terminal of the operational amplifier AMP through the first parallel reverse diode module 11. The bias voltage Vbias is inputted to the second end of the second resistor module 32, and the direct current voltage Vp at the first end of the second resistor module 32 is transmitted to the negative input terminal of the operational amplifier AMP through the second parallel reverse diode module 12. The common-mode voltage of the input and output is separated by the bias voltage and the resistance module voltage division, which ensures the output swing of the operational amplifier AMP and meets the requirements of different input voltages of the common-mode; the first resistor module 31 and the first parallel reverse diode module 11 provide a direct current path for the positive input terminal of the operational amplifier AMP, and the second resistor module 32 and the second parallel reverse diode module 12 provide a direct current path for the negative input terminal of the operational amplifier AMP, to ensure the reliability of the direct current path.

[0025] The operation amplification circuit provided by the embodiment comprises an operation amplifier, a first parallel reverse diode module, a second parallel reverse diode module, a first capacitor module, a second capacitor module, a first resistor module and a second resistor module; wherein the positive input end of the operation amplifier inputs a first voltage, the positive input end of the operation amplifier is electrically connected with the first end of the first parallel reverse diode module, the second end of the first parallel reverse diode module is electrically connected with the first end of the first resistor module, the second end of the first resistor module is connected with a bias voltage, the third end of the first resistor module is electrically connected with the negative output end of the operation amplifier, the positive input end of the operation amplifier is electrically connected with the first end of the first capacitor module, and the second end of the first capacitor module is electrically connected with the negative output end of the operation amplifier; the negative input end of the operation amplifier inputs a second voltage, the negative input end of the operation amplifier is grounded, the negative input end of the operation amplifier is electrically connected with the first end of the second parallel reverse diode module, the second end of the second parallel reverse diode module is electrically connected with the first end of the second resistor module, the second end of the second resistor module is connected with the bias voltage, the third end of the second resistor module is electrically connected with the positive output end of the operation amplifier, the negative input end of the operation amplifier is electrically connected with the first end of the second capacitor module, and the second end of the second capacitor module is electrically connected with the positive output end of the operation amplifier; the common input end of the operation amplifier inputs a common mode voltage. The operation amplification circuit provided by the embodiment provides a direct current path for the positive input end of the operation amplifier through the first resistor module and the first parallel reverse diode module, provides a direct current path for the negative input end of the operation amplifier through the second resistor module and the second parallel reverse diode module, so as to ensure the reliability of the direct current path, and separates the common mode voltage of the input and output through the bias voltage, the first resistor module and the second resistor module, thereby improving the common mode rejection ratio.

[0026] Optionally, the first parallel reverse diode module 11 comprises a first switch tube Q1 and a second switch tube Q2, the first pole of the first switch tube Q1 and the first pole of the second switch tube Q2 serve as the first end of the first parallel reverse diode module 11, the gate of the first switch tube Q1 is electrically connected with the first pole of the first switch tube Q1, the second pole of the first switch tube Q1 and the second pole of the second switch tube Q2 serve as the second end of the first parallel reverse diode module 11, and the gate of the second switch tube Q2 is electrically connected with the second pole of the second switch tube Q2.

[0027] Specifically, as shown in FIG. 1, the operation amplification circuit comprises an operation amplifier 1, a first parallel reverse diode module 11, a second parallel reverse diode module 12, a first capacitor module 21, a second capacitor module 22, a first resistor module 31 and a second resistor module 32. Figure 3As shown, the first terminal of the first switch Q1 and the first terminal of the second switch Q2 are both electrically connected to the positive input terminal of the operational amplifier. When the first switch Q1 and / or the second switch Q2 are turned on, the bias voltage transmitted through the first resistor module to the first parallel reverse diode module 11 is a DC voltage Vp, which is then transmitted to the positive input terminal of the operational amplifier. Therefore, by connecting the first switch Q1 and the second switch Q2 in the first parallel reverse diode module 11 to the positive input terminal of the operational amplifier, a DC path is provided for the positive input terminal of the operational amplifier. Furthermore, the diodes of the first switch Q1 and the second switch Q2 are in opposite directions. These two diodes with opposite directions can both form a DC path and block noise from the first resistor module. The first resistor module can reduce the voltage change across the two diodes, thereby keeping the diodes in a high-impedance state.

[0028] Optionally, the second parallel reverse diode module 12 includes a third switch Q3 and a fourth switch Q4. The first terminals of the third switch Q3 and the fourth switch Q4 serve as the first terminals of the second parallel reverse diode module 12. The gate of the third switch Q3 is electrically connected to the first terminal of the third switch Q3. The second terminals of the third switch Q3 and the fourth switch Q4 serve as the second terminals of the second parallel reverse diode module 12. The gate of the fourth switch Q4 is electrically connected to the second terminal of the fourth switch Q4.

[0029] Specifically, such as Figure 3 As shown, the first terminals of both the third switch Q3 and the fourth switch Q4 are electrically connected to the negative input terminal of the operational amplifier. When the third switch Q3 and / or the fourth switch Q4 are turned on, the bias voltage transmitted through the second resistor module to the second parallel reverse diode module 12 is a DC voltage Vp, which is then transmitted to the negative input terminal of the operational amplifier. Therefore, by connecting the third switch Q3 and the fourth switch Q4 in the second parallel reverse diode module 12 to the negative input terminal of the operational amplifier, a DC path is provided for the negative input terminal of the operational amplifier. Furthermore, the diodes of the third switch Q3 and the fourth switch Q4 are in opposite directions. These two diodes in opposite directions can both form a DC path and block noise from the second resistor module. The second resistor module can reduce the voltage change across the two diodes, thereby keeping the diodes in a high-impedance state.

[0030] Optionally, the first resistor module 31 includes a first resistor R1 and a second resistor R2. The first end of the first resistor R1 serves as the first end of the first resistor module 31, the second end of the first resistor R1 serves as the second end of the first resistor module 31, the first end of the first resistor R1 is electrically connected to the first end of the second resistor R2, and the second end of the second resistor R2 serves as the third end of the first resistor module 31.

[0031] Specifically, as shown in Figure 3 The first end of the first resistor R1 is electrically connected with the second pole of the first switch Q1, the second pole of the second switch Q2 and the first end of the second resistor R2, the second end of the first resistor R1 inputs a bias voltage, and the second end of the second resistor R2 is electrically connected with the negative output end of the operational amplifier. The first resistor R1 and the second resistor R2 divide the bias voltage, and the bias voltage is transmitted to the first parallel reverse diode module after being divided by the first resistor R1.

[0032] Optionally, the voltage at the first end of the first resistor R1 and the voltage at the first end of the second resistor R2 are both (Vbias-Vcm)×R2 / (R1+R2)+Vcm, Vbias is the bias voltage, and Vcm is the common-mode voltage.

[0033] The voltage at the first end of the first resistor R1 and the voltage at the first end of the second resistor R2 are both direct current voltage Vp, that is, Vp=(Vbias-Vcm)×R2 / (R1+R2)+Vcm, and the direct current voltage Vp is transmitted to the positive input end of the operational amplifier through the first parallel reverse diode module.

[0034] Optionally, the second resistor module 32 includes a third resistor R3 and a fourth resistor R4, the first end of the third resistor R3 is the first end of the second resistor module 32, the second end of the third resistor R3 is the second end of the second resistor module 32, the first end of the third resistor R3 is electrically connected with the first end of the fourth resistor R4, and the second end of the fourth resistor R4 is the third end of the second resistor module 32.

[0035] Specifically, as shown in Figure 3 The first end of the third resistor R3 is electrically connected with the second pole of the third switch Q3, the second pole of the fourth switch Q4 and the first end of the fourth resistor R4, the second end of the third resistor R3 inputs a bias voltage, and the second end of the fourth resistor R4 is electrically connected with the negative output end of the operational amplifier. The third resistor R3 and the fourth resistor R4 divide the bias voltage, and the bias voltage is transmitted to the second parallel reverse diode module through the third resistor.

[0036] Optionally, the first capacitor module 21 and the second capacitor module 22 each include a plurality of parallel branches, each branch including a capacitor and a switch connected in series.

[0037] In this configuration, all branches of the first capacitor module 21 are connected between the positive input and negative output of the operational amplifier. By switching these branches on and off, the on / off state of the branch can be controlled, thereby controlling the capacitance value of the capacitor connected between the positive and negative output of the operational amplifier. Similarly, all branches of the second capacitor module 22 are connected between the negative input and positive output of the operational amplifier. By switching these branches on and off, the on / off state of the branch can be controlled, thereby controlling the capacitance value of the capacitor connected between the negative and positive output of the operational amplifier. For example, both the first capacitor module 21 and the second capacitor module 22 include n parallel branches. Capacitor C1 and switch SW1 are located in the same branch, capacitor C2 and switch SW2 are located in the same branch, and capacitor Cn and switch SWn are located in the same branch. The switches in the branches are gain selection switches, that is, the on and off of the switches affect the gain of the operational amplifier Gain=-Cf / Cin, where Cf is the total capacitance of the conducting branches between the positive input terminal and the negative output terminal of the operational amplifier (which is also the total capacitance of the conducting branches between the negative input terminal and the positive output terminal of the operational amplifier, and the two are the same), and Cin is Cin1 (Cin1=Cin2). The gain of the operational amplifier is adjusted by the on and off of the switches in each branch.

[0038] Optionally, the operational amplifier circuit also includes two input capacitors. The positive input terminal of the operational amplifier receives the first voltage VIP through one of the input capacitors, Cin1, and the negative input terminal of the operational amplifier receives the second voltage VIN through the other input capacitor, Cin2.

[0039] Specifically, the input capacitor Cin1 connected to the positive input terminal of the operational amplifier can filter the first voltage VIP, suppress interference noise, and ensure the stability of the voltage transmitted to the positive input terminal of the operational amplifier; the input capacitor Cin2 connected to the negative input terminal of the operational amplifier can filter the second voltage VIN, suppress interference noise, and ensure the stability of the voltage transmitted to the negative input terminal of the operational amplifier.

[0040] Optionally, the resistance value of the first resistor module 31 is the same as the resistance value of the second resistor module 32.

[0041] Specifically, such as Figure 3 As shown, the resistance value of the first resistor in the first resistor module 31 is the same as the resistance value of the third resistor in the second resistor module 32, and the resistance value of the second resistor in the first resistor module 31 is the same as the resistance value of the fourth resistor in the second resistor module 32, so as to ensure that the DC voltage transmitted to the two input terminals of the operational amplifier after the bias voltage passes through the first resistor and the third resistor respectively is equal.

[0042] Optionally, the common-mode voltage Vcm is half of the power supply voltage VDD of the operational amplifier. In this way, the common-mode voltage Vcm is VDD / 2, so that the operational amplifier has a larger output swing.

[0043] In one embodiment, the input resistance R and the feedback resistance Rf are equal. Figure 1 For example, the power supply voltage is 1.5V, the input resistance R and the feedback resistance Rf are equal, and each is 100KΩ; the simulation analysis result is that the output noise is 11.8uV (20-20KHz integration), and the resistance accounts for 90% of the noise contribution. In the operational amplifier circuit in this embodiment, the power supply voltage VDD is 1.5V, the capacitances Cin and Cf are equal, each is 6pF, the resistance in each resistance module is 100kΩ, and Vbias=Vcm; the simulation analysis result is that the output noise is 2.95uV (20-20KHz integration), and the noise contribution is mainly provided by the operational amplifier. In order to further save the area, the resistance in each resistance module can be reduced to 10kΩ, and Vbias=Vcm; the simulation analysis result is that the output noise is 2.95uV (20-20KHz integration), and it will not affect the overall noise performance. In order to improve the output common-mode voltage, the bias voltage Vbias can be increased to 1V, the common-mode voltage Vcm is still VDD / 2, i.e. 0.75V, and other conditions remain unchanged, the simulation analysis result is that the output noise is 3.01uV (20-20KHz integration), and it will not have a significant effect on the overall noise performance. The input DC voltage of the operational amplifier is 0.875V, and the output DC voltage is 0.75V. Changing the DC voltage at the input end of the operational amplifier can be suitable for various operational amplifier structures. When the bias Vbias voltage is grounded, if R1=R2, then Vp is Vcm / 2. The voltage Vp is VONxR1 / (R1+R2)=VON / 2, which reduces the dynamic voltage difference between the switch tubes and suppresses the influence of the output alternating signal on the common-mode signal. The resistance value can be changed so that R1<<R2, which reduces the noise and output swing. When the bias voltage Vbias is input to the common-mode input end of the operational amplifier, there is no current passing through each resistance module when the DC path is established, so there is no power consumption, and the alternating signal during operation also has a suppression effect, which can improve the common-mode voltage suppression effect of the pseudo-differential input. When the bias voltage Vbias is input to each resistance module, the voltage Vp is (Vbias-Vcm)xR2 / (R1+R2)+Vcm, which can be flexibly controlled and also has a common-mode voltage suppression effect.

[0044] In addition, the operational amplifier is a programmable gain operational amplifier. The programmable gain operational amplifier is an operational amplifier with a gain that can be flexibly configured by an external digital signal. The programmable gain operational amplifier integrates the signal amplification function of a traditional operational amplifier and the flexibility of digital control. Without manually replacing resistors or adjusting hardware circuits, the programmable gain operational amplifier can realize rapid switching of different gains and is widely used in scenarios that require dynamic adjustment of signal amplification, such as sensor signal acquisition, industrial automation, and medical device scenarios. The essence of the programmable gain operational amplifier is to change the closed-loop gain of the operational amplifier by digitally controlling the switching of resistors (or capacitors) in the feedback network. The core structure of the programmable gain operational amplifier is based on an operational amplifier and a programmable resistor network. The gain calculation formula is consistent with the closed-loop gain logic of a traditional operational amplifier. The programmable gain operational amplifier is a key device that connects analog signals and digital control. Its core value lies in realizing flexible configuration of gain through digital means.

[0045] Further, the parameters of the programmable gain operational amplifier, such as the programmable gain range, gain accuracy, bandwidth, common mode rejection ratio, affect the working performance of the programmable gain operational amplifier. For example, the programmable gain range of the programmable gain operational amplifier is 1-128 or 0.5-64, the minimum and maximum values of the configurable gain need to cover the dynamic range of the actual signal (for example, a small signal needs high gain, and a large signal needs low gain); the gain accuracy of the programmable gain operational amplifier is the deviation of the actual gain from the theoretical gain (usually represented by ±% or ±ppm), and in a high-precision acquisition scene (such as medical equipment and industrial sensors), a low deviation is required to avoid signal distortion; the bandwidth of the programmable gain operational amplifier is a derived parameter of the gain-bandwidth product, that is, the effective bandwidth under a specific gain, and the higher the gain, the smaller the bandwidth, which needs to be balanced; the greater the common mode rejection ratio of the programmable gain operational amplifier, the better the performance of the circuit, and a higher common mode rejection ratio (such as more than 80 dB) is required in industrial environments and medical equipment to suppress power interference and environmental noise. The programmable gain operational amplifier is irreplaceable in scenarios that require dynamic adaptation of signal amplitude due to its core advantage of programmable gain, and can be applied in sensor signal acquisition, industrial automation and process control, medical electronic equipment, and audio processing scenarios. Sensor signal acquisition (for example, industrial pressure / temperature sensors, medical heart rate sensors, and environmental monitoring gas sensors): The sensor output signal usually has a large dynamic range (for example, a temperature sensor outputs 0-10 mV, and a pressure sensor outputs 0-5 V), and the programmable gain operational amplifier needs to adjust the gain according to the signal amplitude to make the signal match the input range of the analog-to-digital converter (for example, 0-3.3 V), so as to avoid precision loss caused by signal oversaturation or being too small. In an industrial environment (for example, an analog input module of a programmable logic controller and current / voltage detection in motor control), the signal is easily disturbed and has large amplitude fluctuations, and a higher common mode rejection ratio is required to suppress interference and adapt to different range sensors through gain switching (for example, a low-range pressure sensor needs high gain, and a high-range needs low gain). Medical equipment (for example, electrocardiograph, blood pressure monitor, and portable medical detection equipment) has very high requirements for signal accuracy and anti-interference, and the programmable gain operational amplifier needs to have high common mode rejection ratio and low noise characteristics, and at the same time, adapt to the signal strength of different patients through programmable gain. The amplitude of the audio signal of the audio equipment (for example, Bluetooth headset, recording pen, and car audio) changes with the scene (for example, voice signal and music signal), and the programmable gain operational amplifier can realize digital control of the volume (instead of a traditional potentiometer) or adapt to different sensitivity microphones (high-sensitivity microphones need low gain, and low-sensitivity needs high gain) during audio acquisition. The operational amplifier circuit in the embodiment can be applied to a sensor such as a silicon microphone sensor for audio communication.

[0046] The operation amplification circuit provided by the embodiment comprises an operation amplifier, a first parallel reverse diode module, a second parallel reverse diode module, a first capacitor module, a second capacitor module, a first resistor module and a second resistor module. The positive input end of the operation amplifier inputs a first voltage. The positive input end of the operation amplifier is electrically connected with the first end of the first parallel reverse diode module. The second end of the first parallel reverse diode module is electrically connected with the first end of the first resistor module. The second end of the first resistor module is connected with a bias voltage. The third end of the first resistor module is electrically connected with the negative output end of the operation amplifier. The positive input end of the operation amplifier is electrically connected with the first end of the first capacitor module. The second end of the first capacitor module is electrically connected with the negative output end of the operation amplifier. The negative input end of the operation amplifier inputs a second voltage. The negative input end of the operation amplifier is grounded through a capacitor. The negative input end of the operation amplifier is electrically connected with the first end of the second parallel reverse diode module. The second end of the second parallel reverse diode module is electrically connected with the first end of the second resistor module. The second end of the second resistor module is connected with a bias voltage. The third end of the second resistor module is electrically connected with the positive output end of the operation amplifier. The negative input end of the operation amplifier is electrically connected with the first end of the second capacitor module. The second end of the second capacitor module is electrically connected with the positive output end of the operation amplifier. The common-mode input end of the operation amplifier inputs a common-mode voltage. The first parallel reverse diode module comprises a first switch tube and a second switch tube. The second parallel reverse diode module comprises a third switch tube and a fourth switch tube. The first resistor module comprises a first resistor and a second resistor. The second resistor module comprises a third resistor and a fourth resistor. The first capacitor module and the second capacitor module each comprise a plurality of parallel branches. Each branch comprises a capacitor and a switch connected in series. The operation amplification circuit provided by the embodiment provides a direct current path for the positive input end of the operation amplifier through the first resistor module and the first parallel reverse diode module, provides a direct current path for the negative input end of the operation amplifier through the second resistor module and the second parallel reverse diode module, to ensure the reliability of the direct current path, and separates the common-mode voltage of the input and output through the bias voltage, the first resistor module and the second resistor module, to improve the common-mode rejection ratio. Moreover, the setting of the bias voltage can more flexibly design the input voltage of the common-mode without changing the common-mode output voltage, so that the operation amplification circuit is applied to various low-voltage application scenarios. A pair of reverse diodes (diodes in the first parallel reverse diode module) are connected between the first resistor and the second resistor. A pair of reverse diodes (diodes in the second parallel reverse diode module) are connected between the third resistor and the fourth resistor. In a direct current state, the voltage difference of the diodes is zero, and the impedance is very high, so that the noise of the resistor will not be introduced into the output of the operation amplifier. In a working state, the change of the output signal on the diode can be effectively reduced due to the existence of the resistor, so as to reduce the nonlinear influence of the diode impedance.

[0047] Note that the above merely describes preferred embodiments of the present application and the principles of the technology applied. Those skilled in the art will understand that the present application is not limited to the specific embodiments described herein, and that various obvious changes, reconfigurations, combinations and substitutions can be made without departing from the scope of the present application. Therefore, although the present application has been described in detail through the above embodiments, the present application is not limited to the above embodiments, and can include more other equivalent embodiments without departing from the concept of the present application, and the scope of the present application is determined by the scope of the claims.

Claims

1. An operational amplifier circuit characterized by comprising: Comprise: An operational amplifier, a first parallel reverse diode module, a second parallel reverse diode module, a first capacitor module, a second capacitor module, a first resistance module and a second resistance module; Wherein, the positive input end of the operational amplifier inputs a first voltage, the positive input end of the operational amplifier is electrically connected with the first end of the first parallel reverse diode module, the second end of the first parallel reverse diode module is electrically connected with the first end of the first resistance module, the second end of the first resistance module is connected with a bias voltage, the third end of the first resistance module is electrically connected with the negative output end of the operational amplifier, the positive input end of the operational amplifier is electrically connected with the first end of the first capacitor module, and the second end of the first capacitor module is electrically connected with the negative output end of the operational amplifier; The negative input end of the operational amplifier inputs a second voltage, the negative input end of the operational amplifier is grounded through a capacitor, the negative input end of the operational amplifier is electrically connected with the first end of the second parallel reverse diode module, the second end of the second parallel reverse diode module is electrically connected with the first end of the second resistance module, the second end of the second resistance module is connected with the bias voltage, the third end of the second resistance module is electrically connected with the positive output end of the operational amplifier, the negative input end of the operational amplifier is electrically connected with the first end of the second capacitor module, and the second end of the second capacitor module is electrically connected with the positive output end of the operational amplifier; the common mode input end of the operational amplifier inputs a common mode voltage.

2. The operational amplifier circuit according to claim 1, characterized by The first parallel reverse diode module comprises a first switch tube and a second switch tube, the first pole of the first switch tube and the first pole of the second switch tube serve as the first end of the first parallel reverse diode module, the gate of the first switch tube is electrically connected with the first pole of the first switch tube, and the second pole of the first switch tube and the second pole of the second switch tube serve as the second end of the first parallel reverse diode module, and the gate of the second switch tube is electrically connected with the second pole of the second switch tube.

3. The operational amplifier circuit according to claim 1, wherein The second parallel reverse diode module comprises a third switch tube and a fourth switch tube, the first pole of the third switch tube and the first pole of the fourth switch tube serve as the first end of the second parallel reverse diode module, the gate of the third switch tube is electrically connected with the first pole of the third switch tube, the second pole of the third switch tube and the second pole of the fourth switch tube serve as the second end of the second parallel reverse diode module, and the gate of the fourth switch tube is electrically connected with the second pole of the fourth switch tube.

4. The operational amplifier circuit according to claim 1, characterized by The first resistance module comprises a first resistance and a second resistance, the first end of the first resistance serves as the first end of the first resistance module, the second end of the first resistance serves as the second end of the first resistance module, the first end of the first resistance is electrically connected with the first end of the second resistance, and the second end of the second resistance serves as the third end of the first resistance module.

5. The operational amplifier circuit according to claim 4, characterized by The voltage at the first end of the first resistor R1 and the voltage at the first end of the second resistor R2 are both (Vbias-Vcm)×R2 / (R1+R2)+Vcm, Vbias is the bias voltage, and Vcm is the common-mode voltage.

6. The operational amplifier circuit according to claim 1, wherein The second resistor module comprises a third resistor and a fourth resistor, the first end of the third resistor is the first end of the second resistor module, the second end of the third resistor is the second end of the second resistor module, the first end of the third resistor is electrically connected with the first end of the fourth resistor, and the second end of the fourth resistor is the third end of the second resistor module.

7. The operational amplifier circuit according to claim 1, wherein The first capacitor module and the second capacitor module each comprise a plurality of parallel branches, and each branch comprises a capacitor and a switch connected in series.

8. The operational amplifier circuit according to claim 1, wherein The operation amplifier further comprises two input capacitors, one of the input capacitors is connected between the positive input end of the operation amplifier and the first voltage, and the other input capacitor is connected between the negative input end of the operation amplifier and the second voltage.

9. The operational amplifier circuit according to claim 1, wherein The resistance of the first resistor module is the same as the resistance of the second resistor module.

10. The operational amplifier circuit according to claim 1, wherein The common-mode voltage is half of the power voltage of the operation amplifier.

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