CN210041764U - Pre-amplification circuit - Google Patents
Pre-amplification circuit Download PDFInfo
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- CN210041764U CN210041764U CN201921178736.2U CN201921178736U CN210041764U CN 210041764 U CN210041764 U CN 210041764U CN 201921178736 U CN201921178736 U CN 201921178736U CN 210041764 U CN210041764 U CN 210041764U
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Abstract
The utility model discloses a preamplification circuit, including the first order fortune that connects gradually circuit, low pass filter circuit and second level fortune circuit of putting, and with the reference fortune that the circuit input is connected is put to second level fortune. The utility model has the advantages of simple structure and reasonable design and with low costs, be applicable to the mV level little voltage differential signal's in the high common mode voltage environment collection enlarge, the filtering adds front end processing such as direct current biasing, and the practicality is strong.
Description
Technical Field
The utility model belongs to the technical field of the signal processing circuit, concretely relates to preamplification circuit.
Background
The preamplifier circuit is a circuit which is arranged between a signal source and an amplifier stage and is designed for receiving a weak voltage signal from the signal source, but the current preamplifier circuit has some problems:
firstly, the input impedance of the input stage of the prior preamplifier circuit is low, and the input stage of the preamplifier circuit has imbalance, temperature drift and noise, so that the requirements of front-end processing such as acquisition and amplification of mV-level small-voltage differential signals, filtering and direct-current biasing in a high common-mode voltage environment cannot be met;
second, the gain of the second stage operational amplifier circuit of the current preamplifier circuit is fixed and not adjustable, and does not have the function of superimposing a direct current component in an output signal, and offset voltage and temperature drift exist, so that the stability and accuracy of the direct current component are reduced. Therefore, a preamplifier circuit with a simple structure and a reasonable design is lacking at present, and the preamplifier circuit is suitable for front-end processing such as acquisition and amplification, filtering and direct current bias of mV-level small voltage differential signals in a high common-mode voltage environment.
SUMMERY OF THE UTILITY MODEL
The utility model aims to solve the technical problem that not enough among the above-mentioned prior art is directed at, provide a leading amplifier circuit, its simple structure, reasonable in design and with low costs are applicable to the acquisition of the mV level small-voltage differential signal in the high common mode voltage environment and amplify, the filtering adds front end processing such as direct current biasing, and the practicality is strong.
In order to solve the technical problem, the utility model discloses a technical scheme is: a preamplifier circuit, comprising: the circuit comprises a first-stage operational amplifier circuit, a low-pass filter circuit, a second-stage operational amplifier circuit and a reference operational amplifier circuit, wherein the first-stage operational amplifier circuit, the low-pass filter circuit and the second-stage operational amplifier circuit are sequentially connected, and the reference operational amplifier circuit is connected with the input end of the second-stage operational amplifier circuit.
The preamplifier circuit is characterized in that: the low-pass filter circuit is an RC low-pass filter circuit, and the reference operational amplifier circuit is an operational amplifier follower circuit.
The preamplifier circuit is characterized in that: the first-stage operational amplifier circuit comprises a differential amplifier AD8479, the low-pass filter circuit comprises a resistor R6 and a capacitor C1, the second-stage operational amplifier circuit comprises an operational amplifier U2B with the model of LM2904 and an operational amplifier U3A with the model of LM2904, and the reference operational amplifier circuit comprises an operational amplifier U2A with the model of LM 2904.
The preamplifier circuit is characterized in that: the positive phase input end of the differential amplifier AD8479 and the negative phase input end of the differential amplifier AD8479 are connected with the differential voltage signal output end, the output end of the differential amplifier AD8479 is connected with one end of a resistor R6, the other end of the resistor R6 is divided into two paths, one path is grounded through a capacitor C1, and the other path is connected with one end of a resistor R7; the non-inverting input end of the operational amplifier U2B is grounded through a resistor R8, and the inverting input end of the operational amplifier U2B is connected with the other end of the resistor R7; the output end of the operational amplifier U2B is divided into two paths, one path is connected with the inverting input end of the operational amplifier U2B through a variable resistor Rext, and the other path is connected with one end of a resistor R9; the inverting input end of the operational amplifier U3A is connected with the other end of the resistor R9; the output end of the operational amplifier U3A is divided into two paths, one path is connected with the inverting input end of the operational amplifier U3A through a resistor R10, and the other path is the output end of the second-stage operational amplifier circuit; the positive phase input end of the operational amplifier U3A is divided into two paths, one path is grounded through a resistor R12, and the other path is connected with one end of a resistor R11;
the positive phase input end of the operational amplifier U2A is connected with a reference voltage VRin through a resistor R13, the output end of the operational amplifier U2A is divided into three paths, one path is connected with the inverting input end of the operational amplifier U2A through a resistor R14, the other path is connected with the other end of a resistor R11, and the third path is the output end of the reference operational amplifier circuit.
Compared with the prior art, the utility model has the following advantage:
1. the circuit has the advantages of simple structure, reasonable design, fewer components, low cost and small volume.
2. The utility model discloses set up first order operational amplifier circuit, improve and restrain common mode signal ability, improve input impedance, reduce the imbalance in addition, the temperature floats and the noise to can satisfy the collection of the little voltage difference signal of mV level among the high common mode voltage environment and enlarge the processing.
3. The utility model discloses be provided with the variable resistance among the circuit is put to second level fortune, through adjusting the variable resistance, adjust the gain of circuit is put to second level fortune for circuit is put to second level fortune can reach the gain of 1 ~ 10000.
4. The utility model discloses set up reference fortune amplifier circuit, because the normal phase input of reference fortune amplifier circuit and second level fortune amplifier circuit meets for direct current component voltage is added to the alternating current output signal of second level fortune amplifier circuit output, makes output signal become the amplitude and enlargies and add the system's required signal of direct current biasing, realizes stack direct current component function among the output signal, and offset voltage and temperature drift are little.
To sum up, the utility model has the advantages of simple structure and reasonable design and with low costs, be applicable to the mV level little voltage differential signal's among the high common mode voltage environment collection enlargies, the filtering adds front end processing such as direct current biasing, and the practicality is strong.
The technical solution of the present invention is further described in detail with reference to the accompanying drawings and examples.
Drawings
Fig. 1 is a schematic block diagram of the circuit of the present invention.
Fig. 2 is a schematic circuit diagram of the present invention.
Description of reference numerals:
1-first stage operational amplifier circuit; 2-a low-pass filter circuit; 3, a second-stage operational amplifier circuit; 4-reference operational amplifier circuit.
Detailed Description
As shown in fig. 1, the utility model discloses a first order operational amplifier circuit 1, low pass filter circuit 2 and second level operational amplifier circuit 3 that connect gradually, and with reference operational amplifier circuit 4 that second level operational amplifier circuit 3 input is connected.
In this embodiment, the low-pass filter circuit 2 is an RC low-pass filter circuit, and the reference operational amplifier circuit 4 is an operational amplifier follower circuit.
As shown in fig. 2, in this embodiment, the first-stage operational amplifier circuit 1 includes a differential amplifier AD8479, the low-pass filter circuit 2 includes a resistor R6 and a capacitor C1, the second-stage operational amplifier circuit 3 includes an operational amplifier U2B of a model LM2904 and an operational amplifier U3A of a model LM2904, and the reference operational amplifier circuit 4 includes an operational amplifier U2A of a model LM 2904.
As shown in fig. 2, in this embodiment, the non-inverting input terminal of the differential amplifier AD8479 and the inverting input terminal of the differential amplifier AD8479 are connected to the differential voltage signal output terminal, the output terminal of the differential amplifier AD8479 is connected to one end of a resistor R6, the other end of the resistor R6 is divided into two paths, one path is grounded via a capacitor C1, and the other path is connected to one end of a resistor R7; the non-inverting input end of the operational amplifier U2B is grounded through a resistor R8, and the inverting input end of the operational amplifier U2B is connected with the other end of the resistor R7; the output end of the operational amplifier U2B is divided into two paths, one path is connected with the inverting input end of the operational amplifier U2B through a variable resistor Rext, and the other path is connected with one end of a resistor R9; the inverting input end of the operational amplifier U3A is connected with the other end of the resistor R9; the output end of the operational amplifier U3A is divided into two paths, one path is connected with the inverting input end of the operational amplifier U3A through a resistor R10, and the other path is the output end of the second-stage operational amplifier circuit 3; the positive phase input end of the operational amplifier U3A is divided into two paths, one path is grounded through a resistor R12, and the other path is connected with one end of a resistor R11;
the positive phase input end of the operational amplifier U2A is connected with a reference voltage VRin through a resistor R13, the output end of the operational amplifier U2A is divided into three paths, one path is connected with the inverting input end of the operational amplifier U2A through a resistor R14, the other path is connected with the other end of a resistor R11, and the third path is the output end of the reference operational amplifier circuit 4.
In this embodiment, the capacitor C1 is a non-polar capacitor with a capacitance of 4.7 μ F.
In this embodiment, in a specific implementation, the resistance value of the resistor R6 is 5.1k Ω, the resistance values of the resistor R7 and the resistor R8 are both 1k Ω, the resistance values of the resistor R9, the resistor R10, the resistor R11, and the resistor R12 are all 10k Ω, and the resistance values of the resistor R13 and the resistor R14 are both 5.11k Ω.
In this embodiment, in specific implementation, different values of the variable resistor Rext are selected to adjust the voltage gain, so that the gain of the second-stage amplifying circuit 3 can reach 1-10000.
In this embodiment, the resistance value of the variable resistor Rext is further selected to be 16k Ω.
In this embodiment, the reference operational amplifier circuit 4 is arranged because the gain of the reference operational amplifier circuit 4 is 1 and is connected to the positive input terminal of the second stage operational amplifier circuit 2, so that the ac output signal output by the second stage operational amplifier circuit 2 is added with the dc component voltage, the output signal becomes a signal required by a system with amplified amplitude and added with dc bias, the function of superimposing the dc component on the output signal is realized, and the offset voltage and the temperature drift are small.
In this embodiment, the first-stage operational amplifier circuit 1 is provided to improve the ability of suppressing common-mode signals, improve input impedance, and reduce offset, temperature drift and noise, thereby satisfying the requirement of acquiring and processing mV-level small-voltage differential signals in a high common-mode voltage environment.
In this embodiment, the differential amplifier AD8479 is provided because it is a differential amplifier, has high input impedance, has a very high input common mode voltage range, accurately measures a differential voltage signal, and has low offset voltage, low offset voltage drift, low gain drift, low common mode rejection drift, and an excellent common mode rejection ratio, so that it has high gain accuracy, thereby enabling accurate and constant transmission of a small differential mode signal in a high common mode voltage environment.
In this embodiment, the reason why the operational amplifier LM2904 is provided is that it has low input bias current, low input offset voltage, and offset current, wide common mode input voltage range, high gain, and is convenient for realizing amplification of voltage signals.
In this embodiment, the first stage operational amplifier circuit 1 is provided because the first stage operational amplifier circuit 1 has high input impedance, low offset voltage and low offset voltage temperature drift, and an input amplifier having high common mode input voltage has a voltage gain of 1, and can accurately and constantly transmit a small differential mode signal to the first stage operational amplifier circuit 1 for output in a high common mode voltage environment.
In this embodiment, the reference voltage VRin is a 5V reference voltage.
In this embodiment, the output terminal of the reference operational amplifier circuit 4 may also supply power to other power sources.
When the utility model is used, the positive phase input end and the negative phase input end of the first-stage operational amplifier circuit 1 are connected with differential voltage signals, the voltage gain of the first-stage operational amplifier circuit 1 is 1, so that the differential voltage signals are transmitted to the signal output end of the first-stage operational amplifier circuit 1 through difference, the collection of tiny differential voltage signals in a high common-mode voltage environment is adapted, the voltage signals output by the first-stage operational amplifier circuit 1 are sent to the low-pass filter circuit 2, the low-pass filter composed of the resistor R6 and the capacitor C1 filters out high-frequency useless signals in the voltage signals and then sends the filtered voltage signals to the negative phase input end of the operational amplifier U2B in the second-stage operational amplifier circuit 3, the voltage amplification factor of the operational amplifier U2B is 16 times, the operational amplifier U2B in the second-stage operational amplifier circuit 3 firstly performs first-stage amplification on the filtered voltage signals, then sends the voltage amplification signals after the first-stage amplification to the negative phase input end of the operational amplifier U3A, the, the output end of the operational amplifier U3A is connected to the inverting input end of the operational amplifier U3A through a resistor R10, the output end of the operational amplifier U2A is connected to the non-inverting input end of the operational amplifier U3A, and the difference between the voltage after the first-stage amplification and the voltage of the output end of the operational amplifier U2A is the voltage Vout of the output end of the operational amplifier U3A; the operational amplifier U3A in the second-stage operational amplifier circuit 3 performs second-stage amplification on the voltage amplification signal after the first-stage amplification, and after the operational amplifier U2B and the operational amplifier U3A perform two-time phase reversal, a voltage signal in the same phase as the acquired differential voltage signal is obtained, so that acquisition, amplification and filtering processing of the small-voltage differential signal are realized. In the process of the second-stage amplification, the gain of the reference operational amplifier circuit 4 is 1, and the reference operational amplifier circuit is connected with the positive phase input end of the operational amplifier U3A in the second-stage operational amplifier circuit 2, so that the alternating current output signal output by the second-stage operational amplifier circuit 2 is added with direct current component voltage, the output signal becomes a signal required by a system with amplified amplitude and added with direct current bias, the function of superposing the direct current component in the output signal is realized, and offset voltage and temperature drift are small.
The above, only be the utility model discloses a preferred embodiment, it is not right the utility model discloses do any restriction, all according to the utility model discloses the technical entity all still belongs to any simple modification, change and the equivalent structure change of doing above embodiment the utility model discloses technical scheme's within the scope of protection.
Claims (4)
1. A preamplifier circuit, comprising: the circuit comprises a first-stage operational amplifier circuit (1), a low-pass filter circuit (2) and a second-stage operational amplifier circuit (3) which are sequentially connected, and a reference operational amplifier circuit (4) connected with the input end of the second-stage operational amplifier circuit (3).
2. A preamplifier circuit according to claim 1, wherein: the low-pass filter circuit (2) is an RC low-pass filter circuit, and the reference operational amplifier circuit (4) is an operational amplifier following circuit.
3. A preamplifier circuit according to claim 1, wherein: the first-stage operational amplifier circuit (1) comprises a differential amplifier AD8479, the low-pass filter circuit (2) comprises a resistor R6 and a capacitor C1, the second-stage operational amplifier circuit (3) comprises an operational amplifier U2B with the model of LM2904 and an operational amplifier U3A with the model of LM2904, and the reference operational amplifier circuit (4) comprises an operational amplifier U2A with the model of LM 2904.
4. A preamplifier circuit according to claim 3, wherein: the positive phase input end of the differential amplifier AD8479 and the negative phase input end of the differential amplifier AD8479 are connected with the differential voltage signal output end, the output end of the differential amplifier AD8479 is connected with one end of a resistor R6, the other end of the resistor R6 is divided into two paths, one path is grounded through a capacitor C1, and the other path is connected with one end of a resistor R7; the non-inverting input end of the operational amplifier U2B is grounded through a resistor R8, and the inverting input end of the operational amplifier U2B is connected with the other end of the resistor R7; the output end of the operational amplifier U2B is divided into two paths, one path is connected with the inverting input end of the operational amplifier U2B through a variable resistor Rext, and the other path is connected with one end of a resistor R9; the inverting input end of the operational amplifier U3A is connected with the other end of the resistor R9; the output end of the operational amplifier U3A is divided into two paths, one path is connected with the inverting input end of the operational amplifier U3A through a resistor R10, and the other path is the output end of the second-stage operational amplifier circuit (3); the positive phase input end of the operational amplifier U3A is divided into two paths, one path is grounded through a resistor R12, and the other path is connected with one end of a resistor R11;
the positive phase input end of the operational amplifier U2A is connected with a reference voltage VRin through a resistor R13, the output end of the operational amplifier U2A is divided into three paths, one path is connected with the inverting input end of the operational amplifier U2A through a resistor R14, the other path is connected with the other end of a resistor R11, and the third path is the output end of the reference operational amplifier circuit (4).
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201921178736.2U CN210041764U (en) | 2019-07-25 | 2019-07-25 | Pre-amplification circuit |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201921178736.2U CN210041764U (en) | 2019-07-25 | 2019-07-25 | Pre-amplification circuit |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN210041764U true CN210041764U (en) | 2020-02-07 |
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Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN201921178736.2U Active CN210041764U (en) | 2019-07-25 | 2019-07-25 | Pre-amplification circuit |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN210041764U (en) |
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2019
- 2019-07-25 CN CN201921178736.2U patent/CN210041764U/en active Active
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