CN111865262A - Signal conditioning circuit capable of program-controlled compensation - Google Patents
Signal conditioning circuit capable of program-controlled compensation Download PDFInfo
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- CN111865262A CN111865262A CN202010591755.9A CN202010591755A CN111865262A CN 111865262 A CN111865262 A CN 111865262A CN 202010591755 A CN202010591755 A CN 202010591755A CN 111865262 A CN111865262 A CN 111865262A
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H11/00—Networks using active elements
- H03H11/02—Multiple-port networks
- H03H11/40—Impedance converters
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03H—IMPEDANCE NETWORKS, e.g. RESONANT CIRCUITS; RESONATORS
- H03H11/00—Networks using active elements
- H03H11/02—Multiple-port networks
- H03H11/24—Frequency-independent attenuators
Abstract
The embodiment of the application discloses a signal conditioning circuit capable of realizing program-controlled compensation. According to the technical scheme provided by the embodiment of the application, the T-shaped network is arranged on the branch of the impedance transformation network, and the adjustable resistor of the T-shaped network is used for adjusting the low-frequency gain at the feedback end of the operational amplifier, so that the program-controlled adjustment of signals can be realized, and the adjustment effect is optimized. Moreover, the influence of the port capacitance of the digital potentiometer on the circuit bandwidth can be reduced through the T-shaped network, the adjustment error is reduced, and the adjustment effect is further optimized.
Description
Technical Field
The embodiment of the application relates to the technical field of signal conditioning, in particular to a signal conditioning circuit capable of program-controlled compensation.
Background
At present, in instruments such as an oscilloscope and the like, a signal debugging network is arranged to realize impedance transformation and signal attenuation of a circuit. Thus, the high-resistance input can be converted into low-resistance output, and the signal can be reduced to a range acceptable by the semiconductor device. In a conventional signal debugging network, a through network and an attenuation network are generally selected by a relay. When signal attenuation is required, the signal is scaled down by selecting an attenuation network. The attenuation network adopts a resistor to form a voltage division network, and an adjustable capacitor is required to be added in the circuit to compensate the parasitic capacitance due to the adoption of a high-resistance network. However, in the conventional signal debugging network, the adjustable capacitor is a mechanical adjustable capacitor, and needs to be adjusted manually, so that an adjustment error is easily generated, and the adjustment effect is affected.
Disclosure of Invention
The embodiment of the application provides a signal conditioning circuit capable of program-controlled compensation, which can realize program-controlled adjustment of a signal debugging network, reduce adjustment errors and optimize adjustment effects.
The embodiment of the application provides a signal conditioning circuit capable of program-controlled compensation, which comprises a signal input end, a first single-pole double-throw switch, a direct-current branch, an attenuation network branch, a second single-pole double-throw switch, an impedance conversion network branch and a signal output end, wherein the signal input end is connected with the signal conditioning circuit;
the signal input end is connected with a fixed end of the first single-pole double-throw switch, a movable end of the first single-pole double-throw switch is used for selectively connecting a first end of the through branch or a first end of the attenuation network branch, a movable end of the second single-pole double-throw switch is used for selectively connecting a second end of the through branch or a second end of the attenuation network branch, the fixed end of the second single-pole double-throw switch is connected with a first end of the impedance transformation network branch, and a second end of the impedance transformation network branch is connected with the signal output end;
the impedance transformation network branch comprises a first operational amplifier, a first resistor, a second operational amplifier and a T-shaped network, wherein the inverting input end of the first operational amplifier is connected with the first end of the impedance transformation network branch, the non-inverting input end of the first operational amplifier is grounded, and the output end of the first operational amplifier is connected with the first end of the first resistor; the second end of the first resistor is connected with the non-inverting input end of the second operational amplifier, the first end of the second resistor is grounded, the second end of the second resistor is connected with the non-inverting input end of the second operational amplifier and the second end of the first resistor, the inverting input end of the second operational amplifier is connected with the first end of the impedance transformation network branch, and the output end of the second operational amplifier is connected with the second end of the impedance transformation network branch; the T-shaped network comprises a third resistor, an adjustable resistor and a fourth resistor, wherein the first end of the third resistor is connected with the first end of the impedance transformation network branch, the second end of the third resistor is connected with the first end of the adjustable resistor and the first end of the fourth resistor, the second end of the adjustable resistor is grounded, and the second end of the fourth resistor is connected with the second end of the impedance transformation network branch.
Preferably, the impedance transformation network branch further includes a resistance-capacitance series module, a first end of the resistance-capacitance series module is connected to the first end of the impedance transformation network branch, and a second end of the resistance-capacitance series module is connected to the second end of the impedance transformation network branch.
Preferably, the impedance transformation network branch further includes a first resistance-capacitance parallel module, a first end of the first resistance-capacitance parallel module is connected to the first end of the impedance transformation network branch, and a second end of the first resistance-capacitance parallel module is connected to the inverting input end of the first operational amplifier.
Preferably, the impedance transformation network branch further includes a fifth resistor, and the first resistance-capacitance parallel module is connected to the inverting input terminal of the first operational amplifier through the fifth resistor.
Preferably, the impedance transformation network branch further includes a first capacitor, a first end of the first capacitor is connected to the inverting input terminal of the first operational amplifier, and a second end of the first capacitor is connected to the output terminal of the first operational amplifier.
Preferably, the attenuation network branch comprises a sixth resistor, a second capacitor and a second resistance-capacitance parallel module, a first end of the sixth resistor is connected to a first end of the attenuation network branch, a second end of the sixth resistor is connected to a first end of the second capacitor, a second end of the second capacitor is grounded, a first end of the second resistance-capacitance parallel module is connected to a first end of the attenuation network branch, and a second end of the second resistance-capacitance parallel module is connected to a second end of the attenuation network branch.
Preferably, the attenuation network branch further includes a seventh resistor, an eighth resistor and a ninth resistor, the first end of the seventh resistor is connected to the first end of the attenuation network branch, the second end of the seventh resistor is grounded, the first end of the second rc parallel module is connected to the first end of the attenuation network branch through the eighth resistor, and the second end of the second rc parallel module is connected to the second end of the attenuation network branch through the ninth resistor.
Preferably, the circuit further comprises a third resistance-capacitance parallel module, a first end of the third resistance-capacitance parallel module is connected with the signal input end, and a second end of the third resistance-capacitance parallel module is connected with the fixed end of the first single-pole double-throw switch.
Preferably, the signal input end is connected to the first end of the third rc parallel module through a tenth resistor.
Preferably, the third resistance-capacitance parallel module further comprises a third capacitor and a third single-pole double-throw switch, the second end of the third resistance-capacitance parallel module is connected with the fixed end of the first single-pole double-throw switch through the third capacitor, and the third single-pole double-throw switch is connected with the third capacitor in parallel.
According to the signal conditioning circuit capable of realizing program-controlled compensation, the T-shaped network is arranged on the branch of the impedance transformation network, the adjustable resistor of the T-shaped network is used for adjusting the low-frequency gain at the feedback end of the operational amplifier, the program-controlled adjustment of signals can be realized, and the adjustment effect is optimized. Moreover, the influence of the port capacitance of the digital potentiometer on the circuit bandwidth can be reduced through the T-shaped network, the adjustment error is reduced, and the adjustment effect is further optimized.
Drawings
Fig. 1 is a schematic structural diagram of a signal conditioning circuit with programmable compensation according to an embodiment of the present disclosure;
FIG. 2 is an equivalent circuit diagram of a signal conditioning circuit in a through branch gear in the embodiment of the present application;
fig. 3 is an equivalent circuit diagram of the signal conditioning circuit in the attenuation network branch gear in the embodiment of the present application.
Detailed Description
In order to make the objects, technical solutions and advantages of the present application more apparent, specific embodiments of the present application will be described in detail with reference to the accompanying drawings. It is to be understood that the specific embodiments described herein are merely illustrative of the application and are not limiting of the application. It should be further noted that, for the convenience of description, only some but not all of the relevant portions of the present application are shown in the drawings. The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is obvious that all other embodiments obtained by a person of ordinary skill in the art without any creative effort based on the embodiments of the present application belong to the protection scope of the present application. In the embodiments of the present application, the terms "upper", "lower", "left", "right", "front", "rear", "top", "bottom", "inner", "outer", "middle", "vertical", "horizontal", "lateral", "longitudinal", and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings. These terms are used primarily to better describe the present application and its embodiments, and are not used to limit the indicated devices, elements or components to a particular orientation or to be constructed and operated in a particular orientation. Moreover, some of the above terms may be used to indicate other meanings besides the orientation or positional relationship, for example, the term "on" may also be used to indicate some kind of attachment or connection relationship in some cases. The specific meaning of these terms in this application will be understood by those of ordinary skill in the art as appropriate. Furthermore, the terms "mounted," "disposed," "provided," "connected," and "connected" are to be construed broadly. For example, it may be a fixed connection, a removable connection, or a unitary construction; can be a mechanical connection, or an electrical connection; may be directly connected, or indirectly connected through intervening media, or may be in internal communication between two devices, elements or components. The specific meaning of the above terms in the present application can be understood by those of ordinary skill in the art as appropriate. Furthermore, the terms "first," "second," and the like, are used primarily to distinguish one device, element, or component from another (the specific nature and configuration may be the same or different), and are not used to indicate or imply the relative importance or number of the indicated devices, elements, or components. "plurality" means two or more unless otherwise specified.
The application provides a signal conditioning circuit capable of program-controlled compensation, which aims to adjust low-frequency gain at a feedback end of an operational amplifier through an adjustable resistor so as to replace an adjustable capacitor and realize program-controlled adjustment of the signal conditioning circuit. A T-type network is added into a feedback circuit of the operational amplification circuit. The equivalent feedback resistance of the operational amplification circuit can be adjusted by adjusting the adjustable resistance of the T-shaped network, so that the low-frequency gain of the whole circuit is adjusted. For a traditional signal debugging network, an adjustable capacitor is needed for signal adjustment, and the current adjustable capacitor only has the mechanical adjustable capacitor which can meet the indexes of high withstand voltage, low temperature ticket and wide bandwidth, but the mechanical adjustable capacitor can only be adjusted manually, so that manual adjustment is inconvenient and great difference exists. In addition, the mechanical adjustable capacitor adopts the adjustment of the distance between the media to realize capacitance adjustment, which causes the capacitance value of the mechanical adjustable capacitor to change due to factors such as temperature and deformation, thereby affecting the adjustment effect. Therefore, the signal conditioning circuit capable of program-controlled compensation provided by the embodiment of the application is provided to solve the technical problems of debugging errors and poor debugging effect of the existing signal debugging network.
The first embodiment is as follows:
fig. 1 shows a schematic structural diagram of a programmable compensation signal conditioning circuit according to an embodiment of the present application, and referring to fig. 1, the programmable compensation signal conditioning circuit specifically includes: the circuit comprises a signal input end, a first single-pole double-throw switch K2, a through branch, an attenuation network branch, a second single-pole double-throw switch K3, an impedance transformation network branch and a signal output end; the signal input end is connected with the fixed end of the first single-pole double-throw switch K2, the moving end of the first single-pole double-throw switch K2 is used for selectively connecting the first end of the through branch or the first end of the attenuation network branch, the moving end of the second single-pole double-throw switch K3 is used for selectively connecting the second end of the through branch or the second end of the attenuation network branch, the fixed end of the second single-pole double-throw switch K3 is connected with the first end of the impedance transformation network branch, and the second end of the impedance transformation network branch is connected with the signal output end; the impedance transformation network branch comprises a first operational amplifier U2, a first resistor R10, a second resistor R11, a second operational amplifier U1 and a T-shaped network, wherein the inverting input end of the first operational amplifier U2 is connected with the first end of the impedance transformation network branch, the non-inverting input end of the first operational amplifier U2 is grounded, and the output end of the first operational amplifier U2 is connected with the first end of the first resistor R10; a second end of the first resistor R10 is connected to a non-inverting input terminal of the second operational amplifier U1, a first end of the second resistor R11 is grounded, a second end of the second resistor R1 is connected to the non-inverting input terminal of the second operational amplifier U1 and a second end of the first resistor R10, an inverting input terminal of the second operational amplifier U1 is connected to a first end of the impedance transforming network branch, and an output terminal of the second operational amplifier U1 is connected to a second end of the impedance transforming network branch; the T-type network comprises a third resistor R13, an adjustable resistor R15 and a fourth resistor R14, wherein the first end of the third resistor R13 is connected with the first end of the impedance transformation network branch, the second end of the third resistor R13 is connected with the first end of the adjustable resistor R15 and the first end of the fourth resistor R14, the second end of the adjustable resistor R15 is grounded, and the second end of the fourth resistor R14 is connected with the second end of the impedance transformation network branch.
Specifically, in the embodiment of the present application, the impedance transformation network branch provides two operational amplifiers, wherein the second operational amplifier U1 is a high frequency amplifier and serves as a main amplifier. On the basis of the above, a precise operational amplifier, i.e. a first operational amplifier U2, is added. The non-inverting input terminal of the second operational amplifier U1 is not directly connected to the ground, but connected to the output terminal of the first operational amplifier U2. Therefore, in the low frequency band, the first operational amplifier U2 utilizes its high open loop gain to adjust the level of the inverting input terminal of the second operational amplifier U1 to keep the level at 0 all the time, thereby affecting the offset and gain of the low frequency band signal. The impedance transformation network branch circuit is realized by adopting the high-speed operational amplifier and the high-precision operational amplifier together, and can be compatible with the characteristics of low-frequency precision and high bandwidth.
In addition, a first single-pole double-throw switch K2 and a second single-pole double-throw switch K3 are arranged at two ends of the straight-through branch and the attenuation network branch, so that the attenuation switching network of the two-stage switch is formed. The damping switching network may provide different damping steps. The connection mode of the first single-pole double-throw switch K2 and the second single-pole double-throw switch K3 is switched according to requirements, and the straight-through branch or the attenuation network branch is conducted to realize different attenuation step signal attenuation. Due to the adoption of the attenuation switching network of the front and rear two-stage switches (namely the first single-pole double-throw switch K2 and the second single-pole double-throw switch K3), the high-frequency gain does not need to add an additional high-frequency compensation module at the operational amplifier end. It should be noted that, in the embodiment of the present application, the attenuation network may be set to be one stage or multiple stages according to the actual signal attenuation requirement.
Preferably, the impedance transformation network branch further includes a resistance-capacitance series module, a first end of the resistance-capacitance series module is connected to the first end of the impedance transformation network branch, and a second end of the resistance-capacitance series module is connected to the second end of the impedance transformation network branch. The resistance-capacitance series module is connected in parallel at two ends of the T-shaped network and comprises a resistor R12 and a capacitor C6 which are connected in series, wherein C6 is a capacitor with a low capacitance value and the capacitance value is 1-20 pF, and the high-frequency characteristic of the resistor connected in parallel is compensated. R12 is a small resistance resistor with a resistance value of 0-200 omega, and is used for adjusting the gain of partial high-frequency band.
Preferably, the impedance transformation network branch further includes a first rc parallel module, a first end of the first rc parallel module is connected to the first end of the impedance transformation network branch, and a second end of the first rc parallel module is connected to the inverting input end of the first operational amplifier U2. The first resistance-capacitance parallel module comprises a resistor R3 and a capacitor C2, wherein R3 is a large-resistance resistor with the resistance value of 40-200K omega, and is used for realizing attenuation of direct current signals. C2 is a capacitor with large capacitance between 50pF and 200pF to compensate the high frequency characteristic of its parallel resistor.
Further, the impedance transformation network branch further comprises a fifth resistor R9, and the first rc parallel module is connected to the inverting input terminal of the first operational amplifier U2 through the fifth resistor R9. The impedance transformation network branch further comprises a first capacitor C5, wherein a first end of the first capacitor C5 is connected with the inverting input end of the first operational amplifier U2, and a second end is connected with the output end of the first operational amplifier U2. Specifically, during signal processing, after passing through the parallel network of the first rc parallel module, the signal flows into the inverting input terminal of the first operational amplifier U2 through the fifth resistor R9, is amplified by the first operational amplifier U2, and then is output to the first resistor R10. While the signal flows through the first capacitor C5 to the output of the first operational amplifier U2U 2. Then, the signal is divided by a voltage division resistor network formed by a first resistor R10 and a second resistor R11 and then input to the non-inverting input end of a second operational amplifier U1, so that the impedance transformation function of the impedance transformation network is realized.
Preferably, the attenuation network branch comprises a sixth resistor R6, a second capacitor C3 and a second rc parallel module, a first end of the sixth resistor R6 is connected to the first end of the attenuation network branch, a second end of the sixth resistor R3 is connected to the first end of the second capacitor C3, a second end of the second capacitor C3 is grounded, a first end of the second rc parallel module is connected to the first end of the attenuation network branch, and a second end of the second rc parallel module is connected to the second end of the attenuation network branch. The sixth resistor R6 is a small resistance resistor with a resistance value of 0 Ω -200 Ω, and is used for adjusting gain of a part of high-frequency band. The second capacitor C3 is a capacitor with a larger capacitance value between 50pF and 200pF to compensate the high frequency characteristic of the parallel resistor. The second resistance-capacitance parallel module comprises a resistor R7 and a capacitor C4, wherein the resistor R7 is a large-resistance resistor with the resistance value of 300K omega-1M omega, and is used for attenuation of direct current signals. The capacitor C4 is a low-capacitance capacitor with a capacitance between 1pF and 20pF to compensate the high-frequency characteristics of its parallel resistor.
Preferably, the attenuation network branch further includes a seventh resistor R4, an eighth resistor R5, and a ninth resistor R8, a first end of the seventh resistor R4 is connected to the first end of the attenuation network branch, a second end of the seventh resistor R4 is grounded, a first end of the second rc parallel module is connected to the first end of the attenuation network branch through the eighth resistor R5, and a second end of the second rc parallel module is connected to the second end of the attenuation network branch through the ninth resistor R8. The seventh resistor R4 is a large-resistance resistor with a resistance value of 40K omega-200K omega, and is used for attenuation of direct current signals. The eighth resistor R5 and the ninth resistor R8 are small-resistance resistors with the resistance value of 0-200 omega, and are used for adjusting the gain of a part of high-frequency band.
Preferably, the switch further comprises a third rc parallel module, a first end of the third rc parallel module is connected to the signal input end, and a second end of the third rc parallel module is connected to the stationary end of the first single-pole double-throw switch K2. The third rc parallel module comprises a resistor R2 and a capacitor C1, wherein the resistor R2 is a large-resistance resistor for attenuation of dc signals. The capacitor C1 is a low-capacitance capacitor with a capacitance between 1pF and 20pF to compensate the high-frequency characteristics of its parallel resistor. The attenuation network branch gear and the straight-through branch gear share a parallel circuit with a large resistance value and a small capacitance, so that the input parameter error between the gears can be reduced.
Preferably, the signal input terminal may be a BNC terminal, a first end of the BNC terminal is grounded, and a second end of the BNC terminal is connected to the first end of the third rc parallel module through a tenth resistor. The tenth resistor is a small-resistance resistor with the resistance value of 0 omega-200 omega and is used for adjusting the gain of a part of high-frequency bands. It should be noted that the signal input end in the embodiment of the present application may be different signal terminals according to different application scenarios, and specific signal terminals are not fixedly limited in the embodiment of the present application, which is not described herein repeatedly.
Preferably, the third resistor-capacitor parallel module further comprises a third capacitor C9 and a third single-pole double-throw switch K1, the second end of the third resistor-capacitor parallel module is connected to the fixed end of the first single-pole double-throw switch K2 through the third capacitor C9, and the third single-pole double-throw switch K1 is connected in parallel with the third capacitor C9. The third capacitor C9 is an ultra-large capacitance value capacitor with the capacitance value of 10 nF-100 nF. And, a third single-pole double-throw switch K1 is arranged to provide an AC coupling position of the circuit. When the third single-pole double-throw switch K1 is turned off and the circuit is in the ac coupling position, the blocking effect on the dc signal can be achieved through the third capacitor C9.
The T-shaped network is arranged on the impedance transformation network branch, and the adjustable resistor R15 of the T-shaped network is used for adjusting the low-frequency gain at the feedback end of the operational amplifier, so that the program control adjustment of signals can be realized, and the adjustment effect can be optimized. Moreover, the influence of the port capacitance of the digital potentiometer on the circuit bandwidth can be reduced through the T-shaped network, the adjustment error is reduced, and the adjustment effect is further optimized.
Specifically, referring to fig. 1, a specific process of signal processing of the signal conditioning circuit with programmable compensation according to the embodiment of the present application is provided. Wherein the signal is input through the BNC terminal, through the resistor R1, and into the parallel network of capacitors C1 and R2. The signal then goes to a parallel network of K1 and C9 and then to the single pole double throw switch K2. After entering the SPDT K2K2, the signal can be selected by the SPDT K2 for different branches. If the hardware is in the through gear, the single-pole double-throw switch K2 sends a signal directly into the single-pole double-throw switch K3. If the hardware is in the attenuation position, switch K2 sends the signal into the lower attenuation network branch. When the signal enters the attenuation network branch, the signal is firstly input to the ground by R4 and is simultaneously transmitted to the rear stage by R5. After passing through R5, the signal reaches the intersection of R6 and R7. The signal passes through R6, into C3, and finally into ground. At the same time, the signal flows into R8 and finally into the relay K3 through the parallel network of R7 and C4. When the hardware is in a straight-through branch gear, the single-pole double-throw switch K3 selects a signal flowing from K2, and when the hardware is in an attenuation network branch, the single-pole double-throw switch K3 selects a signal flowing from R8. K3 eventually flows the signal into a parallel network of C2 and R3. After passing through the parallel network of C2 and R3, the signal flows through R9 to the inverting input of operational amplifier U2, is amplified by operational amplifier U2 to R10, and at the same time, the signal flows through C5 to the output of operational amplifier U2. Then, the signal passes through a voltage division resistor network formed by R10 and R11, and is input to the non-inverting input end of the operational amplifier U1 after voltage division. The signal passes through a parallel network of C2 and R3, reaches the inverting input terminal of an operational amplifier U1, is amplified by an operational amplifier U1, and reaches the signal output terminal analog output. The signal reaches R13 after passing through the parallel network of C2 and R3. After passing through R13, the signal reaches the intersection of R15 and R14. The signal flows through an adjustable resistor R15 to ground. And meanwhile, the analog output is reached to a signal output end through R14. The signal reaches R12 after passing through the parallel network of C2 and R3. After passing through R12, it reaches C6, and after passing through C6, it reaches the signal output terminal analog output.
In the above, a T-type network is added to the feedback circuit of the operational amplifier circuit. The equivalent feedback resistance of the operational amplifier circuit is: (1+ R14/R15). times.R 13; the equivalent feedback resistance of the amplification circuit can be adjusted by adjusting R15, thereby adjusting the low frequency gain of the overall circuit. The T-shaped network is adopted to reduce the influence of the capacitance of the ground port of the digital potentiometer on the bandwidth of the circuit.
Specifically, when the circuit is in the through branch gear, the equivalent circuit diagram of the signal conditioning circuit with programmable compensation in the embodiment of the present application refers to fig. 2, wherein, since R2 and R3 are large-resistance resistors, and their resistances far exceed R1 and R12, their dc gain is: (1+ R14/R15). times.R 13/(R2+ R3). The dc gain can be adjusted by R15 to match the ac gain, but C1 × R2 is required to be C2 × R3.
On the other hand, when the circuit is in the attenuation network branch gear, the equivalent circuit diagram of the signal conditioning circuit with programmable compensation according to the embodiment of the present application refers to fig. 3, where, as in the direct-through network, the dc gain is mainly affected by the large resistance. Therefore, the DC gain was R4 × (1+ R14/R15). times.R 13/((R2+ R3) × (R4+ R7+ R3)). The dc gain can be tuned by R15 to match the ac gain. But requires C1 xr 2 ═ R4 xc 3 ═ R7 xc 4 ═ R3 xc 2. And R4 × (R7+ R3)/(R4+ R7+ R3) ═ R3 is required.
When the direct branch is in the through branch gear, the input resistance is R2+ R3, and the input capacitance is (C1 × C2)/(C1+ C2). When the attenuation network branch is in the gear, the input resistance of the attenuation network is R2+ R3 because R4 × (R7+ R3)/(R4+ R7+ R3) ═ R3. Since C1 × R2 ═ R4 × C3 ═ R7 × C4 ═ R3 × C2, the input capacitance is (C1 × Ce)/(C1+ Ce). Wherein Ce ═ C3+ C4 × C2/(C4+ C2). Since C1 is a capacitor with a small capacitance value and Ce is a capacitor with a large capacitance value, the total capacitance value is greatly influenced by C1, so that the error between the input capacitance and the direct-connection network is very small.
It should be noted that the small resistance responsible for adjusting the high frequency gain is different based on the different attenuation steps. In the through branch gear, the small resistors responsible for adjusting the high-frequency gain are R1 and R12, and in the attenuation network branch gear, the small resistors responsible for adjusting the high-frequency gain are R1, R5, R6, R8 and R12. This allows for more flexible adjustment of the high frequency gain without the need for additional programmable compensation networks.
Compared with the traditional signal debugging network, the embodiment of the application adopts the program-controlled adjustable resistor to adjust, so that full-automatic adjustment can be realized. The consistency and the accuracy of measurement can be improved, and automatic compensation after delivery is facilitated. However, since the conventional mechanical tunable capacitor is adjusted only when the housing of the product is opened, the tuning effect is deteriorated after the product is aged, and the tuning effect cannot be automatically adjusted, so that the tuning effect may be gradually deteriorated with the change of the use time, and the tuning effect is difficult to recover without returning to the factory. In addition, because the third resistance-capacitance parallel module is shared, the error of the input parameters between different gears is very small, and the signal adjusting precision and the adjusting effect can be further optimized.
The foregoing is considered as illustrative of the preferred embodiments of the invention and the technical principles employed. The present application is not limited to the particular embodiments described herein, but is capable of various obvious changes, rearrangements and substitutions as will now become apparent to those skilled in the art without departing from the scope of the invention. Therefore, although the present application has been described in more detail with reference to the above embodiments, the present application is not limited to the above embodiments, and may include other equivalent embodiments without departing from the spirit of the present application, and the scope of the present application is determined by the scope of the claims.
Claims (10)
1. A programmable compensated signal conditioning circuit, comprising: the circuit comprises a signal input end, a first single-pole double-throw switch, a direct-connection branch, an attenuation network branch, a second single-pole double-throw switch, an impedance transformation network branch and a signal output end;
the signal input end is connected with a fixed end of the first single-pole double-throw switch, a movable end of the first single-pole double-throw switch is used for selectively connecting a first end of the through branch or a first end of the attenuation network branch, a movable end of the second single-pole double-throw switch is used for selectively connecting a second end of the through branch or a second end of the attenuation network branch, the fixed end of the second single-pole double-throw switch is connected with a first end of the impedance transformation network branch, and a second end of the impedance transformation network branch is connected with the signal output end;
The impedance transformation network branch comprises a first operational amplifier, a first resistor, a second operational amplifier and a T-shaped network, wherein the inverting input end of the first operational amplifier is connected with the first end of the impedance transformation network branch, the non-inverting input end of the first operational amplifier is grounded, and the output end of the first operational amplifier is connected with the first end of the first resistor; the second end of the first resistor is connected with the non-inverting input end of the second operational amplifier, the first end of the second resistor is grounded, the second end of the second resistor is connected with the non-inverting input end of the second operational amplifier and the second end of the first resistor, the inverting input end of the second operational amplifier is connected with the first end of the impedance transformation network branch, and the output end of the second operational amplifier is connected with the second end of the impedance transformation network branch; the T-shaped network comprises a third resistor, an adjustable resistor and a fourth resistor, wherein the first end of the third resistor is connected with the first end of the impedance transformation network branch, the second end of the third resistor is connected with the first end of the adjustable resistor and the first end of the fourth resistor, the second end of the adjustable resistor is grounded, and the second end of the fourth resistor is connected with the second end of the impedance transformation network branch.
2. The programmable compensated signal conditioning circuit of claim 1, wherein the impedance transforming network branch further comprises a series resistor-capacitor module having a first end connected to the first end of the impedance transforming network branch and a second end connected to the second end of the impedance transforming network branch.
3. The programmable compensated signal conditioning circuit of claim 1, wherein the impedance transforming network branch further comprises a first rc parallel module, a first end of the first rc parallel module is connected to the first end of the impedance transforming network branch, and a second end of the first rc parallel module is connected to the inverting input of the first operational amplifier.
4. The programmable compensated signal conditioning circuit of claim 3, wherein the impedance transforming network branch further comprises a fifth resistor, and the first RC parallel module is connected to the inverting input terminal of the first operational amplifier through the fifth resistor.
5. The programmable compensated signal conditioning circuit of claim 4, wherein the impedance transforming network branch further comprises a first capacitor having a first terminal connected to the inverting input terminal of the first operational amplifier and a second terminal connected to the output terminal of the first operational amplifier.
6. The programmable compensated signal conditioning circuit of claim 1, wherein the attenuation network branch comprises a sixth resistor, a second capacitor and a second rc parallel module, a first end of the sixth resistor is connected to the first end of the attenuation network branch, a second end of the sixth resistor is connected to the first end of the second capacitor, a second end of the second capacitor is grounded, a first end of the second rc parallel module is connected to the first end of the attenuation network branch, and a second end of the second rc parallel module is connected to the second end of the attenuation network branch.
7. The programmable compensated signal conditioning circuit of claim 6, wherein the attenuation network branch further comprises a seventh resistor, an eighth resistor, and a ninth resistor, a first end of the seventh resistor is connected to the first end of the attenuation network branch, a second end of the seventh resistor is connected to ground, a first end of the second RC parallel module is connected to the first end of the attenuation network branch through the eighth resistor, and a second end of the second RC parallel module is connected to the second end of the attenuation network branch through the ninth resistor.
8. The programmable compensated signal conditioning circuit of claim 1, further comprising a third rc parallel module having a first end connected to the signal input end and a second end connected to the stationary end of the first single-pole double-throw switch.
9. The programmable compensated signal conditioning circuit of claim 8, wherein the signal input terminal is connected to the first terminal of the third rc parallel module through a tenth resistor.
10. The programmable compensated signal conditioning circuit of claim 8, further comprising a third capacitor and a third SPDT switch, wherein the second terminal of the third RC parallel module is connected to the stationary terminal of the first SPDT switch through the third capacitor, and the third SPDT switch is connected in parallel with the third capacitor.
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