Isolation amplification circuit

Abstract

The application discloses an isolation amplification circuit, comprising: a signal input end and a signal output end, further comprising: a signal attenuation unit, an input end of the signal attenuation unit being connected with the signal input end; an isolation unit, an input end of the isolation unit being connected with an output end of the signal attenuation unit; a multi-stage signal amplification unit, cascaded between the output end of the isolation unit and the signal output end; wherein an amplification multiple of each stage of the signal amplification unit is less than an attenuation multiple of the signal attenuation unit. The input signal is first attenuated by the signal attenuation unit to prevent saturation of the signal transmission signal, and the input signal is attenuated to a low voltage suitable for the multi-stage signal amplification unit by the signal attenuation unit, so that the offset accumulation of each subsequent stage of the signal amplification unit is effectively reduced. The multi-stage signal amplification unit is gradually amplified, so that the wide frequency characteristic is maintained at a low gain.

Description

Technical Field

[0001] This application relates to the field of signal transmission technology, specifically to an isolation amplifier circuit. Background Technology

[0002] With the increasing demands for high-frequency signal processing from measuring instruments, communication equipment, and industrial automation systems (such as bandwidths above 50MHz), and the increasingly stringent requirements for signal conversion accuracy (low offset, low temperature drift) and dynamic range (amplitude voltage conversion), traditional single-stage amplifier circuits or simple multi-stage amplifier schemes are gradually revealing their performance bottlenecks.

[0003] While traditional single-stage amplifier circuits offer a wide bandwidth, their limited single-stage gain (typically voltage gain <100) makes it difficult to directly amplify high-amplitude signals. Furthermore, the offset voltage (mV level) and temperature drift after single-stage amplification can easily lead to insufficient output accuracy. While cascading multi-stage amplifier circuits can increase gain, it suffers from two major problems: First, the superposition of poles across multiple stages significantly compresses the total bandwidth, making it difficult to meet the requirements for distortion-free amplification of high-frequency signals. Second, the cumulative effect of the offset voltage from the preceding stage after being amplified by the gain product of subsequent stages is significant (e.g., a 1mV offset in the first stage becomes 100mV after cascading with a 100x gain), and the temperature drift amplifies exponentially with increasing stage number, causing distortion in the output signal and severely affecting its stability.

[0004] Therefore, how to achieve high-bandwidth, low-distortion signal transmission has become an urgent technical problem to be solved. Utility Model Content

[0005] In view of this, this application provides an isolation amplifier circuit to solve the technical problem of how to achieve high bandwidth and low distortion signal transmission in related technologies.

[0006] This application provides an isolation amplifier circuit, including: a signal input terminal and a signal output terminal, and further including: a signal attenuation unit between the signal input terminal and the signal output terminal, the input terminal of the signal attenuation unit being connected to the signal input terminal; an isolation unit, the input terminal of the isolation unit being connected to the output terminal of the signal attenuation unit; and a multi-stage signal amplification unit, wherein the input terminal of the first-stage signal amplification unit is connected to the output terminal of the isolation unit, and the output terminal of the last-stage signal amplification unit is connected to the signal output terminal; wherein the amplification factor of each stage signal amplification unit is less than the attenuation factor of the signal attenuation unit.

[0007] In one embodiment, the signal attenuation unit includes: a first operational amplifier, a first input resistor, and a first feedback resistor, wherein the signal input terminal is connected to the first input terminal of the first operational amplifier through the first input resistor, the second input terminal of the first operational amplifier is grounded, the output terminal of the first operational amplifier is connected to the first input terminal through the first feedback resistor, and the output terminal of the first operational amplifier is connected to the input terminal of the frequency divider unit, and the resistance value of the first feedback resistor is less than the resistance value of the first input resistor.

[0008] In one embodiment, the first operational amplifier includes an AD8061 operational amplifier.

[0009] In one embodiment, the multi-stage signal amplification unit includes a first-stage signal amplification unit and a second-stage signal amplification unit, wherein the input terminal of the first-stage signal amplification unit is connected to the output terminal of the isolation module unit, the output terminal of the first-stage signal amplification unit is connected to the input terminal of the second-stage signal amplification unit, and the output terminal of the second-stage signal amplification unit is connected to the signal output terminal.

[0010] In one embodiment, the first-stage signal amplification unit includes: a second operational amplifier, a second input resistor, and a second feedback resistor, wherein the output terminal of the isolation unit is connected to the first input terminal of the second operational amplifier through the second input resistor, the second input terminal of the second operational amplifier is grounded, the output terminal of the second operational amplifier is connected to the first input terminal through the second feedback resistor, and the output terminal of the second operational amplifier is connected to the signal output terminal, and the resistance value of the second feedback resistor is greater than the resistance value of the second input resistor.

[0011] In one embodiment, the second-stage signal amplification unit includes a third operational amplifier, a third input resistor, and a third feedback resistor. The output terminal of the first-stage signal amplification unit is connected to the first input terminal of the third operational amplifier through the third input resistor. The second input terminal of the third operational amplifier is grounded. The output terminal of the third operational amplifier is connected to the first input terminal through the third feedback resistor, and the output terminal of the third operational amplifier is connected to the signal output terminal. The resistance value of the third feedback resistor is greater than the resistance value of the third input resistor.

[0012] In one embodiment, the second operational amplifier includes an AD8099 operational amplifier, and the third operational amplifier includes a THS3091 operational amplifier.

[0013] In one embodiment, a calibration circuit is provided between the second operational amplifier and the third operational amplifier for zero-point leveling and temperature drift compensation.

[0014] In one embodiment, the calibration circuit includes an adjustable potentiometer and a fixed resistor connected between a power supply or ground, wherein the resistance adjustment terminal of the adjustable potentiometer is connected to the second input terminal of the third operational amplifier.

[0015] In one embodiment, the signal attenuation unit has an attenuation factor of K, the first-stage signal amplification unit has an amplification factor of N, and the second-stage signal amplification unit has an amplification factor of M, wherein K = M × N, and K, N, and M are all greater than 1.

[0016] This application has at least the following beneficial effects: The isolation amplifier circuit in this application includes a signal attenuation unit between the signal input and signal output terminals, with the input terminal of the signal attenuation unit connected to the signal input terminal; an isolation unit, with its input terminal connected to the output terminal of the signal attenuation unit; and a multi-stage signal amplification unit, wherein the input terminal of the first-stage signal amplification unit is connected to the output terminal of the isolation unit, and the output terminal of the last-stage signal amplification unit is connected to the signal output terminal; wherein the amplification factor of each stage signal amplification unit is less than the attenuation factor of the signal attenuation unit. The signal attenuation unit first attenuates the input signal to prevent saturation when directly fed into the multi-stage signal amplification unit for high gain. By attenuating the input signal to a low voltage suitable for the multi-stage signal amplification unit, the multi-stage signal amplification unit can operate in the center of the linear region, avoiding saturation and reducing the amplification factor of the input offset voltage, effectively reducing the offset of each stage of the signal amplification unit and effectively reducing the offset accumulation of subsequent stages. The first stage of the multi-stage signal amplification unit processes low-amplitude signals, while the last stage restores high-amplitude output, balancing the accuracy of small signals with the dynamic range of large signals. Furthermore, the multi-stage signal amplification unit amplifies the signal step by step, maintaining wideband characteristics at low gain. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the specific embodiments of this application or the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0018] Figure 1 This is a modular schematic diagram of the isolation amplifier circuit provided according to an embodiment of this application; Figure 2 This is a schematic diagram of the signal attenuation unit in the isolation amplifier circuit provided in the embodiments of this application; Figure 3 This is a schematic diagram of the circuit principle of the first-stage signal amplification unit in the isolation amplifier circuit provided according to the embodiments of this application; Figure 4 This is a schematic diagram of the circuit principle of the second-stage signal amplification unit in the isolation amplifier circuit provided according to the embodiments of this application; Figure 5 This is a schematic diagram of the calibration circuit in the isolation amplifier circuit provided according to the embodiments of this application. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0020] According to an embodiment of this application, an isolation amplifier circuit is provided, such as... Figure 1 As shown, the system includes a signal input terminal 10 and a signal output terminal 50. Between the signal input terminal 10 and the signal output terminal 50, it further includes: a signal attenuation unit 20, the input terminal of which is connected to the signal input terminal 10; an isolation unit 30, the input terminal of which is connected to the output terminal of the signal attenuation unit 20; and a multi-stage signal amplification unit 40, wherein the input terminal of the first-stage signal amplification unit is connected to the output terminal of the isolation unit 30, and the output terminal of the last-stage signal amplification unit is connected to the signal output terminal 50; wherein the amplification factor of each stage signal amplification unit is less than the attenuation factor of the signal attenuation unit 20.

[0021] In this embodiment, the input signal is first attenuated by the signal attenuation unit 20 to prevent saturation when directly fed into the multi-stage signal amplification unit 40 for high gain. By attenuating the input signal to a low voltage suitable for the multi-stage signal amplification unit 40 through the signal attenuation unit 20, the multi-stage signal amplification unit 40 can operate in the center of the linear region, avoiding saturation and reducing the amplification factor of the input offset voltage. It can also effectively reduce the offset of each stage of the signal amplification unit. For example, if the offset voltage of the signal attenuation unit 20 is 1mV, after 20 times attenuation, the subsequent multi-stage signal amplification unit only needs to handle a deviation of 0.05mV, which can effectively reduce the offset accumulation of the subsequent stages of the signal amplification unit. Furthermore, by having the first stage of the multi-stage signal amplification unit 40 process the low-amplitude signal and the last stage restore the high-amplitude output, it balances the accuracy of small signals with the dynamic range of large signals. Moreover, by performing step-by-step amplification through the multi-stage signal amplification unit 40, it achieves wideband characteristics at low gain.

[0022] In one embodiment, such as Figure 2 As shown, the signal attenuation unit 20 includes: a first operational amplifier U1, a first input resistor R1, and a first feedback resistor Rf1. The signal input terminal 10 is connected to the first input terminal of the first operational amplifier U1 through the first input resistor R1. The second input terminal of the first operational amplifier U1 is grounded. The output terminal of the first operational amplifier U1 is connected to the first input terminal through the first feedback resistor Rf1, and the output terminal of the first operational amplifier U1 is connected to the input terminal of the isolation unit 30. The resistance value of the first feedback resistor Rf1 is less than the resistance value of the first input resistor R1. The attenuation factor of the first operational amplifier 21 is -R. f1 / R1, where R f1 Rf1 is the resistance value of the first feedback resistor, and R1 is the resistance value of the first input resistor R1. In this embodiment, the resistance value of the first feedback resistor Rf1 can be 20 times the resistance value of the first input resistor R1, achieving a 20-fold signal attenuation. Of course, the attenuation factor can be adjusted by changing the resistance values ​​of the first feedback resistor Rf1 and the first input resistor R1, which can meet the needs of various application scenarios.

[0023] In this embodiment, the first operational amplifier U1 can be an AD8061 operational amplifier, which attenuates the external input signal, such as ±10V, to a low voltage of ±0.5V suitable for subsequent amplification stages. The first operational amplifier U1 has high impedance and a large bandwidth. The high input impedance can reduce the signal source load effect, making it suitable for high internal resistance signal sources. The gain-bandwidth product is ≥50MHz, which can ensure that the signal attenuation unit has no significant amplitude-frequency attenuation within 50MHz.

[0024] In one embodiment, the multi-stage signal amplification unit 40 includes a first-stage signal amplification unit 41 and a second-stage signal amplification unit 42. The input terminal of the first-stage signal amplification unit 41 is connected to the output terminal of the isolation module unit 30, the output terminal of the first-stage signal amplification unit 41 is connected to the input terminal of the second-stage signal amplification unit 42, and the output terminal of the second-stage signal amplification unit 42 is connected to the signal output terminal 50. The first-stage signal amplification unit 41 performs preliminary amplification of the attenuated signal to reduce noise introduction, while the second-stage signal amplification unit 42 restores the high-amplitude output of the pre-amplified signal, balancing small-signal accuracy with large-signal dynamic range.

[0025] In this embodiment, the attenuation factor of the signal attenuation unit 20 is K, the amplification factor of the first-stage signal amplification unit 41 is N, and the amplification factor of the second-stage signal amplification unit 42 is M, where K = M × N, and K, N, and M are all greater than 1. For example, the attenuation factor K of the signal attenuation unit 20 is 20, and the product of the amplification factor N of the first-stage signal amplification unit 41 and the amplification factor M of the second-stage signal amplification unit 42 is 20. In one embodiment, to maintain wideband characteristics as much as possible, the amplification factor of each stage is kept to a relatively small value to minimize bandwidth compression in high-gain bands and ensure the overall bandwidth of the isolation amplifier circuit. For example, the amplification factor N of the first-stage signal amplification unit 41 can be 5, and the amplification factor of the second-stage signal amplification unit 42 can be 4. Of course, in optional embodiments, other combinations of amplification factors can also be selected.

[0026] In this embodiment, the first-stage signal amplification unit 41 includes: a second operational amplifier U2, a second input resistor R2, and a second feedback resistor Rf2. The output terminal of the isolation unit 30 is connected to the first input terminal of the second operational amplifier U2 via the second input resistor R2. The second input terminal of the second operational amplifier U2 is grounded. The output terminal of the second operational amplifier U2 is connected to the first input terminal via the second feedback resistor Rf2, and the output terminal of the second operational amplifier U2 is connected to the signal output terminal 50. The resistance value of the second feedback resistor Rf2 is greater than the resistance value of the second input resistor R2. The greater resistance value of the second feedback resistor Rf2 than the second input resistor R2 achieves signal amplification. In this embodiment, both in-phase and inverting amplification can be used. This embodiment uses an inverting amplification circuit as an example for explanation. The second input resistor R2 is connected to the inverting input terminal of the second operational amplifier U2, and the second feedback resistor Rf2 is connected between the output terminal and the inverting input terminal of the second operational amplifier U2. The amplification factor of the second operational amplifier U2 is: -Rf2. f2 / R2, where R f2Rf2 is the resistance value of the second feedback resistor, and R2 is the resistance value of the second input resistor R2. In this embodiment, the resistance value of the second input resistor R2 can be 5 times the resistance value of the second feedback resistor Rf2, achieving an initial amplification of 5 times. Of course, by adjusting the resistance values ​​of the second feedback resistor Rf2 and the second input resistor R2, the amplification factor can be increased to meet the needs of various application scenarios.

[0027] In this embodiment, the second operational amplifier U2 can be an AD8099 operational amplifier, which amplifies the attenuated signal with approximately a gain of 5, reducing noise introduction and ensuring that the signal maintains low offset and noise at low amplitude. The AD8099 operational amplifier has an input voltage noise of 1.2nV / √Hz, suppressing noise amplification in the preceding stage and is suitable for amplifying weak signals. It also has a high gain-bandwidth product ≥250MHz, maintaining a 50MHz bandwidth at 5x gain, meeting the frequency response requirements of the intermediate stage.

[0028] In one embodiment, a compensation capacitor C1 is connected in series in the feedback loop of the second operational amplifier U2 of the first-stage signal amplification unit 41 to adjust the pole position, avoid the bandwidth drop caused by the superposition of multiple poles, and achieve a staggered tuning effect.

[0029] The second-stage signal amplification unit 42 includes a third operational amplifier U3, a third input resistor R3, and a third feedback resistor Rf3. The output terminal of the first-stage signal amplification unit 41 is connected to the first input terminal of the third operational amplifier U3 via the third input resistor R3. The second input terminal of the third operational amplifier U3 is grounded. The output terminal of the third operational amplifier U3 is connected to the first input terminal via the third feedback resistor Rf3, and the output terminal of the third operational amplifier U3 is connected to the signal output terminal 50. The resistance value of the third feedback resistor Rf3 is greater than the resistance value of the third input resistor R3. The greater resistance value of the third feedback resistor Rf3 compared to the third input resistor R3 allows for further signal amplification. In this embodiment, both in-phase and inverting amplification can be used. This embodiment uses an inverting amplification circuit as an example for explanation. The third input resistor R3 is connected to the inverting input terminal of the third operational amplifier U3, and the third feedback resistor Rf3 is connected between the output terminal and the inverting input terminal of the third operational amplifier U3. The amplification factor of the third operational amplifier U3 is: -R f3 / R3, where R f3Rf3 is the resistance value of the third feedback resistor, and R3 is the resistance value of the third input resistor. In this embodiment, the resistance value of the third input resistor R3 can be four times the resistance value of the third feedback resistor Rf3, achieving a preliminary amplification of four times. Of course, by adjusting the resistance values ​​of the third feedback resistor Rf3 and the third input resistor R3, the amplification factor can be increased to meet the needs of various application scenarios.

[0030] In this embodiment, the third operational amplifier U3 can be a THS3091 operational amplifier, which has a high slew rate greater than 6000V / μs, supports high-frequency large signal fast conversion, and avoids phase distortion. Furthermore, it has a signal bandwidth of 135MHz, ensuring stable output amplitude within 100MHz, ensuring no significant output signal distortion, and meeting high-frequency requirements.

[0031] In one embodiment, a calibration circuit 43 is provided between the second operational amplifier U2 and the third operational amplifier U3 for zero-point leveling and temperature drift compensation. The calibration circuit 43 adjusts the DC bias to compensate for the inherent offset of each operational amplifier stage. Simultaneously, the calibration circuit 43 exhibits high consistency with temperature changes, reducing the accumulation of temperature drift from one stage to the next, thus achieving inter-stage temperature compensation.

[0032] The calibration circuit 43 may include an adjustable potentiometer R4 and a fixed resistor R connected between a power supply and ground. The resistance adjustment terminal of the adjustable potentiometer R4 is connected to the second input terminal of the third operational amplifier U3. In this embodiment, the adjustable potentiometer R4 and the fixed resistor R are connected between the positive and negative power supplies, and the resistance adjustment terminal of the adjustable potentiometer R4 is connected to the second input terminal of the third operational amplifier U3. By adjusting the resistance value of the adjustable potentiometer R4, the DC bias of the input signal is changed, thereby adjusting the zero bias of the signal. Simultaneously, the adjustable potentiometer R4 and the fixed resistor R are high-precision resistors, which have high consistency with temperature changes, further reducing temperature drift accumulation.

[0033] In the above embodiments of this application, the descriptions of each embodiment have different focuses. For parts not described in detail in a certain embodiment, please refer to the relevant descriptions of other embodiments.

[0034] The above are merely preferred embodiments of this application. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of this application, and these improvements and modifications should also be considered within the scope of protection of this application.

Claims

1. An isolation amplifier circuit, characterized in that, include: A signal input terminal and a signal output terminal, wherein the signal input terminal and the signal output terminal are further comprising: A signal attenuation unit, wherein the input terminal of the signal attenuation unit is connected to the signal input terminal; An isolation unit, wherein the input terminal of the isolation unit is connected to the output terminal of the signal attenuation unit; A multi-stage signal amplification unit, wherein the input terminal of the first stage signal amplification unit is connected to the output terminal of the isolation unit, and the output terminal of the last stage signal amplification unit is connected to the signal output terminal; In this case, the amplification factor of each signal amplification unit is less than the attenuation factor of the signal attenuation unit.

2. The isolation amplifier circuit as described in claim 1, characterized in that, The signal attenuation unit includes a first operational amplifier, a first input resistor, and a first feedback resistor. The signal input terminal is connected to the first input terminal of the first operational amplifier through the first input resistor. The second input terminal of the first operational amplifier is grounded. The output terminal of the first operational amplifier is connected to the first input terminal through the first feedback resistor. The output terminal of the first operational amplifier is also connected to the input terminal of the isolation unit. The resistance value of the first feedback resistor is less than the resistance value of the first input resistor.

3. The isolation amplifier circuit as described in claim 2, characterized in that, The first operational amplifier includes the AD8061 operational amplifier.

4. The isolation amplifier circuit as described in claim 1, characterized in that, The multi-stage signal amplification unit includes a first-stage signal amplification unit and a second-stage signal amplification unit. The input terminal of the first-stage signal amplification unit is connected to the output terminal of the isolation unit, the output terminal of the first-stage signal amplification unit is connected to the input terminal of the second-stage signal amplification unit, and the output terminal of the second-stage signal amplification unit is connected to the signal output terminal.

5. The isolation amplifier circuit as described in claim 4, characterized in that, The first-stage signal amplification unit includes a second operational amplifier, a second input resistor, and a second feedback resistor. The output terminal of the isolation unit is connected to the first input terminal of the second operational amplifier through the second input resistor. The second input terminal of the second operational amplifier is grounded. The output terminal of the second operational amplifier is connected to the first input terminal through the second feedback resistor, and the output terminal of the second operational amplifier is connected to the signal output terminal. The resistance value of the second feedback resistor is greater than the resistance value of the second input resistor.

6. The isolation amplifier circuit as described in claim 5, characterized in that, The second-stage signal amplification unit includes a third operational amplifier, a third input resistor, and a third feedback resistor. The output terminal of the first-stage signal amplification unit is connected to the first input terminal of the third operational amplifier through the third input resistor. The second input terminal of the third operational amplifier is grounded. The output terminal of the third operational amplifier is connected to the first input terminal through the third feedback resistor, and the output terminal of the third operational amplifier is connected to the signal output terminal. The resistance value of the third feedback resistor is greater than the resistance value of the third input resistor.

7. The isolation amplifier circuit as described in claim 6, characterized in that, The second operational amplifier includes an AD8099 operational amplifier, and the third operational amplifier includes a THS3091 operational amplifier.

8. The isolation amplifier circuit as described in claim 6, characterized in that, A calibration circuit is provided between the second operational amplifier and the third operational amplifier for zero-point leveling and temperature drift compensation.

9. The isolation amplifier circuit as described in claim 8, characterized in that, The calibration circuit includes an adjustable potentiometer and a fixed resistor connected between a power supply or ground, wherein the resistance adjustment terminal of the adjustable potentiometer is connected to the second input terminal of the third operational amplifier.

10. The isolation amplifier circuit as described in claim 4, characterized in that, The signal attenuation unit has an attenuation factor of K, the first-stage signal amplification unit has an amplification factor of N, and the second-stage signal amplification unit has an amplification factor of M, where K = M × N, and K, N, and M are all greater than 1.

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