Instrumentation amplifier

FIELD: radio engineering, communication.

SUBSTANCE: instrumentation amplifier comprises: an input precision converter of (1) of a first (2) and a second (3) input voltage source connected to a common power supply bus (4), a first (9), a second (10) and a third (11) feedback resistor, an active adder (12) with an inverting (13) and a non-inverting (14) input.

EFFECT: high coefficient of attenuation of input in-phase voltage and eliminating the in-phase component in output signals of operational amplifiers, which improves efficiency of the amplitude characteristic thereof.

4 cl, 26 dwg

The present invention relates to the field of measurement technology, radio engineering, communications and can be used as a device for precision amplification of analog signals in the circuits of various functional purposes (e.g., for measuring and automatic systems, medical technology, diagnostics and so on).

Creating analog and analog-to-digital interfaces of mixed systems on chip (SOC), focused on the interaction with the sensing elements (sensors) bridge type always involves the use of instrumentation amplifiers (in-amps) with fixed and controllable parameters, performs the function of suppressing the common-mode voltage and amplifying a differential voltage. These devices are the basis for analog ports, and for a whole class of difficult-functional blocks (SF units) SOC. A sufficiently large dynamic range of measured values and relatively high conversion accuracy predupredili the use of such interfaces precision operational amplifiers (op-amp). Most of the currently known solutions associated with classical structure built Yiwu, consisting of three OS and a set of precision resistors [1-16].

The closest prototype of the proposed device is the local amplifier, presented in the patent US 2010/0259323 A1 1 author Paul L. Bugyik. It contains the input precision Converter 1 of the first 2 and second 3 sources of input voltages associated with the common power bus 4, the first 5 and second 6 outputs the input precision of the Converter 1, the first 7 and second 8 inputs of the device associated with the first 2 and second 3 sources of input voltages, the first 9 and second 10 and third resistors 11 feedback, active adder 12 13 inverting and reinvestiruet 14 inputs, the output device 15 associated with the output of the active adder 12, and the first 5 output input precision of the Converter 1 is connected with the inverting input 13 active the adder 12, the second 6 output input precision of the Converter 1 is connected with reinvestiruet entrance 14 active adder 12.

Significant disadvantages of the known device, the architecture of which is also present in many other instrumental amplifiers [1-16], are as follows:

1. The first drawback. Even when using strictly identical operational amplifiers in the structure of the input precision of the Converter 1, the limit of attenuation of the input common-mode signal (K_CH) will be determined by the following ratio:

$$K_{\mathrm{with\; a}n}=\frac{R_{}}{R_3+R_4}(1+\frac{R_1}{R_2})-\frac{R_1}{R_2}=\frac{R_4-R_3\frac{R_1}{R_2}}{R_3+R_4},\text{(1)}$$

where R₁÷R₄resistors included in the structure of the active accumulator (12) figure 1.

Therefore, a profound weakening of the input common mode signal in Yiwu figure 1 is possible only when strictly agreed resistors R₁÷R₄.

It can be shown that even with implementation of the conditions of strict identity of resistance (R₁=R₂=R₃=R₄=R) K_CHnot better than

$$K_{\mathrm{with\; a}n\min }=\Delta K_{\mathrm{with\; a}n}={\Theta }_R,\text{(2)}$$

where Θ_R- accuracy resistor active is umutara (12) (figure 1).

Thus, from the above expressions (1) and (2) shows that the maximum realizable rejection input common-mode signal PS 1 is limited by the accuracy of the resistances of the resistors of the active adder Θ_R. As a consequence, even for precision technologies, in which Θ_R=0.1%, the attenuation coefficient of the input common-mode voltage Yiwu figure 1 does not exceed 60 dB, which is clearly not enough to build even nprecision measuring and sensor systems. Therefore, in the manufacture of such schemes Yiwu use expensive precision laser tuning resistors R₁÷R₄aimed at the achievement of the required quality indicators resistors (e.g., Θ_R=0,01%), in which the attenuation of the input common-mode signal does not exceed 75 dB.

2. The second drawback. The inefficient use of the passing characteristics of the first (A1) and second (A2) of the operational amplifiers in the structure of the PS 1. This is because (the main part of the amplitude characteristics of the first (A1) and second (A2) operational amplifiers contains a component input common-mode voltage

$$U_{A1}=U_{\mathrm{with\; a}n}-\frac{R_9}{R_{11}}$$

where U_A1and U_A2the voltage at the output of the first (A1) and second (A2) operational amplifiers, respectively, U_CH- a common-mode voltage at the inputs of the instrumental amplifier 7 and 8, U_ddifferential voltage at the inputs of the instrumental amplifier 7 and 8, R₉÷R₁₁resistors the feedback circuit included in the structure of the input precision of the Converter 1 1.

The main objectives of the present invention are as follows. 1. To exclude precision resistors R₁÷R₄from the structure of the active adder 12 and, hence, the need for costly precision laser settings of these resistors. This will not only increase product yield in the production, but also to maximize the attenuation of the input common-mode voltage in the structure of Yiwu.

2. To eliminate in-phase component of the output signals of the first (A1) and second (A2) operational amplifiers that will enhance effective is the efficiency of the use of their amplitude characteristics.

The problem is solved in that in the instrumentation amplifier figure 1, containing the input precision Converter 1 of the first 2 and second 3 sources of input voltages associated with the common power bus 4, the first 5 and second 6 outputs the input precision of the Converter 1, the first 7 and second 8 inputs of the device associated with the first 2 and second 3 sources of input voltages, the first 9 and second 10 and third resistors 11 feedback, active adder 12 13 inverting and reinvestiruet 14 inputs, the output device 15 associated with the output of the active adder 12, and the first 5 output input precision of the Converter 1 is connected with the inverting input 13 of the active adder 12, the second 6 output input precision of the Converter 1 is connected with reinvestiruet entrance 14 active adder 12, there are new elements and connections - input precision Converter 1 includes a first Converter 15 "voltage-current", the inverting input of which is connected with the first 7 input device, and a non-inverting input is connected with the second 8-input device, the first 16 current output of the first Converter 15 "voltage-current" is connected with the first 17 current output of the second Converter 18 "voltage-current" and is connected to the not inverting current the first input 19 output Converter "current-voltage" and in asteroidea current to the second input 20 output Converter "current-voltage", the second current output 21 of the first Converter 15 "voltage-current" 22 connected to the second current output of the second Converter 18 "voltage-current" and is connected to the inverting current input of the first 19 output Converter "current-voltage" and not inverting current input 20 second output Converter "current-voltage", and the signal on the first 16 current output of the first Converter 15 "voltage-current" anti-phase signal 21 on the second current output of the first Converter 15 "voltage-current", and the signal on the first 17 current output of the second Converter 18 "voltage-the current" anti-phase signal 22 on the second current output of the second Converter 18 "voltage-current" and common-mode signals on the first 16 current output of the first Converter 15 "voltage-current", the output 23 of the first 19 output Converter "current-voltage" is connected with the first 5 output input precision of the Converter 1, and is connected with the inverting input of the second Converter 18 "voltage-current" 10 through the second feedback resistor, and the inverting input of the second Converter 18 "voltage-current" is connected to the common bus power supply 4 via the optional feedback resistor 24 the output 25 of the second 20 output Converter "current-voltage" is connected with the second 6 output input precision what about the Converter 1, and also associated with reinvestiruet input of the second Converter 18 "voltage-current" through the first 9 feedback resistor, and the non-inverting input of the second Converter 18 "voltage-current" is connected to the common bus power supply 4 through 11 third feedback resistor.

The scheme of the instrumental amplifier prototype shown in the drawing figure 1.

In the drawing figure 2 presents the diagram of the inventive device in accordance with claim 1, and in the drawing figure 3 in accordance with claim 2. In the drawing figure 4 presents a simplified graphic image input precision of the Converter 1, corresponding to claim 1 of the claims. In the drawing figure 5 presents a simplified graphical image of the active adder 12, corresponding to claim 2.

In the drawing, 6 represents the diagram Yiwu, the corresponding clause 3 of the claims and in the drawing 7 - corresponding to claim 4 claims.

In the drawing Fig is a diagram of connections of the inventive instrumental amplifier 2 in the PSpice environment on component models of bipolar and field analog base matrix crystal ABMK, which was used to study its main properties.

In the drawing figure 9 shows the diagram of the inventive instrumental amplifier 6 in the environment PSpice models compound is bipolar and field analog base matrix crystal ABMK, which was used to study its main characteristics (Fig-26).

In the drawing figure 10 and 11 shows respectively the logarithmic amplitude - and phase-frequency characteristics differential gain of the voltage of the instrumental amplifier Fig for different values of the resistances of the feedback resistors in the structure of the input precision of the Converter (1) figure 2 determining realized the value of this factor.

On Fig shows the frequency dependence of the transfer ratio input common-mode voltage of the instrumental amplifier Fig (figure 2) at different values of the differential conversion gain voltage (K_d=20 dB, 40 dB, 60 dB).

In the drawing Fig the graphs of the boundary voltages at the outputs (5) and (6) the input precision of the Converter (1) when applying the differential signal at the inputs (7) and (8) of the device Fig (figure 2), for different values of the differential conversion gain voltage (K_d=20 dB, 40 dB, 60 dB).

In the drawing Fig shows the values of the voltage drift at the output (15) of the instrumental amplifier Fig (2) when the temperature changes from -40 to +85 degrees Celsius.

In the drawing Fig shows a histogram that displays the possible values of the voltage zero drift instrumental stress the El Fig (2) the application of the Monte Carlo method (Gaussian distribution, the change of attitude of the resistors of 0.1%), and in the drawing Fig - histogram reflecting the possible values of the transfer ratio input common-mode voltage in a similar situation.

In the drawing Fig the graphs rejection ratio input common-mode voltage of the instrumental amplifier Fig (figure 2) using the method of Monte Carlo (Gaussian distribution, the change of attitude of the resistors of 0.1%).

In the drawing Fig - Fig shown respectively logarithmic amplitude - and phase-frequency characteristics differential gain of the voltage of the instrumental amplifier figure 9 for different values of the resistances of the feedback resistors in the structure of the input precision of the Converter 1 6 determining realized the value of this coefficient. In the drawing Fig the characteristic differential gain of the voltage of the instrumental amplifier in Fig.9 bandwidth.

On Fig shows the frequency dependence of the transfer ratio input common-mode voltage of the instrumental amplifier Fig.9 (6) for different values of the differential conversion gain voltage (K_d=20 dB, 40 dB, 60 dB).

In the drawing Fig the graphs of the boundary voltages at the outputs (5) and (6) input the th precision of the Converter (1) when applying the differential signal at the inputs (7) and (8) of the device Fig.9 (6) for different values of the differential conversion gain voltage (KD=20 dB, 40 dB, 60 dB).

In the drawing Fig shows the values of the voltage drift at the output (15) of the instrumental amplifier Fig.9 (6) when the temperature changes from -40 to +85 degrees Celsius.

In the drawing Fig shows a histogram that displays the possible values of the voltage zero drift instrumental amplifier Fig.9 (6) the result of applying the Monte Carlo method (Gaussian distribution, the change of attitude of the resistors of 0.1%), and in the drawing Fig - histogram reflecting the possible values of the transfer ratio input common-mode voltage in a similar situation.

In the drawing Fig the graphs rejection ratio input common-mode voltage of the instrumental amplifier Fig.9 (6) using the method of Monte Carlo (Gaussian distribution, the change of attitude of the resistors of 0.1%).

Graphics Fig - Fig (PS 2) and Fig - Fig (PS figure 3) show that the claimed device, in contrast to Yiwu 1, characterized by high attenuation of the input common-mode signal, weakly dependent on the errors of the resistive elements. This will avoid expensive laser precision tuning resistors and, therefore, increase product yield during production. In addition, the voltage of the zero drift of the instrumental amplifier defined voltage is receiving zero offset active adder 12, as seen on Fig (PS 2) and Fig (PS 6), also has a low dependence on the errors of the resistive elements.

Instrumental amplifier figure 2 contains the input precision Converter 1 of the first 2 and second 3 sources of input voltages associated with the common power bus 4, the first 5 and second 6 outputs the input precision of the Converter 1, the first 7 and second 8 inputs of the device associated with the first 2 and second 3 sources of input voltages, the first 9 and second 10 and third resistors 11 feedback, active adder 12 13 inverting and reinvestiruet 14 inputs, the output device 15 associated with the output of the active adder 12, and the first 5 output input precision of the Converter 1 is connected with the inverting input 13 active adder 12, the second 6 output input precision of the Converter 1 is connected with nevertrust entrance 14 active adder 12. Input precision Converter 1 includes a first Converter 15 "voltage-current", the inverting input of which is connected with the first 7 input device, and a non-inverting input is connected with the second 8-input device, the first 16 current output of the first Converter 15 "voltage-current" is connected with the first 17 current output of the second Converter 18 "voltage-current" and is connected to the not inverting current input of the first 19 output convert what the user "current-voltage" and to the inverting current input 20 second output Converter "current-voltage", the second current output 21 of the first Converter 15 "voltage-current" 22 connected to the second current output of the second Converter 18 "voltage-current" and is connected to the inverting current input of the first 19 output Converter "current-voltage" and not inverting current input 20 second output Converter "current-voltage", and the signal on the first 16 current output of the first Converter 15 "voltage-current" anti-phase signal 21 on the second current output of the first Converter 15 "voltage-current", and the signal on the first 17 current output of the second Converter 18 "voltage-the current" anti-phase signal 22 on the second current output of the second Converter 18 "voltage-current" and common-mode signals on the first 16 current output of the first Converter 15 "voltage-current", the output 23 of the first 19 output Converter "current-voltage" is connected with the first 5 output input precision of the Converter 1, and is connected with the inverting input of the second Converter 18 "voltage-current" 10 through the second feedback resistor, and the inverting input of the second Converter 18 "voltage-current" is connected to the common bus power supply 4 via the optional feedback resistor 24 the output 25 of the second 20 output Converter "current-voltage" is connected with the second 6 output input precision what about the Converter 1, and also associated with reinvestiruet input of the second Converter 18 "voltage-current" through the first 9 feedback resistor, and the non-inverting input of the second Converter 18 "voltage-current" is connected to the common bus power supply 4 through 11 third feedback resistor.

In the drawing figure 3, in accordance with claim 2, the active adder 12 26 includes a third inverter "voltage-current", inverting input connected to the output device 15, and the non-inverting input connected with a common bus power sources 4, the fourth Converter 27 "voltage-current", the inverting input of which is connected to the inverting input 13 of the active adder 12, the non-inverting input connected to the not inverting input 14 of the active adder 12, the first 28 current output of the third Converter 26 "voltage-current" is connected with the first 29 current output of the fourth Converter 27 "voltage-current, and is connected to a not inverting current input of the third 30 output Converter "current-voltage", 31 second current output of the third Converter 26 "voltage-current" is connected with the second 32 current output of the fourth Converter 27 "voltage-current" and is connected to the inverting current input of the third 30 output Converter "current-voltage", and the signal on the first 28 current output tert what his 26 Converter "voltage-current" anti-phase signal 31 on the second current output of the third Converter 26 "voltage-current", and the signal on the first 29 current output of the fourth Converter 27 "voltage-current" anti-phase signal 32 on the second current output of the fourth Converter 27 "voltage-current" and the common mode signal on the first 28 current output of the third Converter 26 "voltage-current".

In the drawing figure 4, in accordance with paragraph 1 of the claims, provides a simplified graphical image input precision of the Converter 1, in which the elements 15, 18, 19, 20 is conventionally marked active element 33.

In the drawing figure 5, in accordance with claim 2, shown is a simplified graphical depiction of the active adder 12, in which the elements 26, 27, 30 is conventionally marked active element 34.

In the drawing 6, in accordance with section 3 of the claims, the first 5 output input precision of the Converter 1 is connected with the inverting input 13 of the active adder 12 through the first 35 low pass filter having an inlet 37 and outlet 38, and the second 6 output input precision of the Converter 1 is connected with reinvestiruet entrance 14 active adder 12 36 through the second low pass filter having an inlet 39 and outlet 40. Each of the low-pass filters 35, 36 includes serially connected resistors 41, 42, 43, an amplifier 44, and capacitors 45, 46, 47.

In the drawing 7, in accordance with paragraph 4 of the claims, the first 5 of the 6 second outputs of the input precision of the Converter 1 are connected to the corresponding inverting 13 and reinvestiruet 14 active inputs of the adder 12 through the differential input (antiphase inputs 49, 50) and the differential output (out-of-phase outputs 51, 52) low pass filter 48.

Consider the work of PS 2.

The signal containing the common-mode and differential components, is fed to the inverting 7 (VH) and non-inverting 8 (VH) inputs input precision of the Converter 1 and fed to the inverting and non-inverting inputs of the first Converter 15 "voltage-current", respectively. Through the implementation of high attenuation common-mode component of the input signal in the input differential amplifier stage of the first Converter 15 "voltage-current" is the suppression of the common mode component of the signal is increased the amplitude of the differential component of the signal according to the selected relationship of the first (9) and third (11)and second (10) and additional (24) of the resistors of the feedback circuit. Enhanced differential component of the input signal together with weakened in relation to the input in-phase component signal, and the error introduced by voltage drift output (23) of the first (19) the output of the Converter current-voltage and output (25) of the second (20) output Converter "current-voltage", proceed to the exit (5) and outlet (6) input precision transducer (1) and then by inverting$$(Bx{.}_{\Sigma 1}^{(-)})$$(13) and noninverting$$(Bx{.}_{\Sigma 1}^{(+)})$$(14) the active inputs of the adder (12) respectively, where is the subtraction of the incoming signals, which can significantly reduce the error introduced in the output voltage of zero drift input transducer (1), and to reduce the transfer ratio input common-mode voltage (with input precision of the Converter (1) within a single crystal and a single process), and the summation of the amplified differential voltage. Moreover attenuated in-phase component of the input signal and the voltage drift of the zero outputs of (23) and (25) of the first (19) and second (20) input converters "current-voltage" to the inverting and powertrade inputs of the second (18) Converter "voltage-current", respectively, are perceived as a common-mode voltage, the suppressed due to the implementation of high attenuation common-mode component of the input signal in the input di is ferentially cascades second (18) Converter "voltage-current". Finally, at the output of the active accumulator (12) and output device (15), you receive the amplified differential signal with the error defined by the voltage zero offset active accumulator (12).

We show analytically that the above properties of the instrumental amplifier are implemented in the inventive scheme 2.

Indeed, using the methods of analysis of electronic circuits it is possible to show that the proposed instrumental amplifier (figure 2) is characterized by the following parameters:

The amplification factor of the differential signal

$$K_d=\frac{2}{\frac{R_{24}}{R_{24}+R_{10}}+\frac{R_{11}}{R_{11}+R_9}},\text{(4)}$$

therefore, the choice of relationship denominations of the first (9) R₉and third (11) R₁₁the feedback resistors, and the second (10) R₁₀resistor feedback and additional (24) R₂₄the feedback resistor sets the value of the parameter K_dinstrumental amplifier (figure 2). In particular, we can use the equality R₁₁=R_{24/sub> =r and R9=R10=R, then}

$$K_d=1+\frac{R}{r}.\text{(5)}$$

Transfer ratio common-mode voltage of the instrumental amplifier:

$$K_{\mathrm{with\; a}n}=2\cdot K_d\cdot K_{\mathrm{about}\mathrm{with\; a}\mathrm{with\; a}n1}\cdot K_{\mathrm{about}\mathrm{with\; a}\mathrm{with\; a}n12},\text{(6)}$$

where K_Assn- attenuation of common mode voltage, which is implemented in the input converters "voltage-current" (15, 18) of the input precision of the Converter (1), K_Assn- attenuation of common mode voltage of the active accumulator (12) (figure 2).

Voltage zero drift instrumental amplifier is determined by the ratio:

$$U_{dp.\mathrm{And}Y}=\left(U_{dp.5}-U_{dp.6}\right)\cdot K_{\mathrm{about}\mathrm{with\; a}\mathrm{with\; a}n12}+U_{dp.12},\text{(7)}$$

where U_drew- voltage zero drift instrumental amplifier, U_Drand U_Drthe voltage drift at the output (5) and outlet (6) of the input precision of the Converter (1), respectively, U_Dr- voltage zero drift of the active accumulator (12). Taking into account the input of the precision of the Converter (1) (2) in a single process within a single crystal U_Dr=U_Dr:

$$U_{dp.\mathrm{And}Y}=U_{dp.12}=K_{d.12}\cdot E_{\mathrm{with\; a}m.12},\text{(8)}$$

where K₁₂- gain differential signal of the active accumulator (12), E_sm- EMF offset of the active accumulator (12) (figure 5). As the active accumulator (12) is used as the adder signals (K₁₂=1):

$$U_{dp.\mathrm{And}Y}=E_{\mathrm{with\; a}m.12}.\text{the (9)}$$

Thus, the voltage of the zero drift of the instrumental amplifier is determined by the EMF bias of the active accumulator (12).

Voltage outputs (5) and (6) the input precision of the Converter (1):

$$U_5=K_{\mathrm{about}\mathrm{with\; a}\mathrm{with\; a}n1}\cdot U_{\mathrm{with\; a}n}-\frac{R_{10}}{R_{24}}\cdot \frac{U_d}{2},{\text{U}}_{\text{6}}=K_{\mathrm{about}\mathrm{with\; a}\mathrm{with\; a}n1}\cdot U_{\mathrm{with\; a}n}+\frac{R_9}{R_{11}}\cdot \frac{U_d}{2}.\text{(10)}$$

Thus, when K_Assn<<1 increases the efficiency of the use of amplitude characteristics of the outputs (5) and (6) input precision transducer (1) (2). Indeed, in the device-prototype (figure 1):

$$U_{A1}=U_{\mathrm{with\; a}n}-\frac{R_9}{R_1}{U}_d,{\text{U}}_{\text{A2}}=U_{\mathrm{with\; a}n}+\frac{R_{10}}{R_{11}}{U}_d,\text{(11)}$$

these stresses are determined by the common-mode voltage at the input of the instrumental amplifier U_CH.

In addition, the prototype (figure 1):

$$U_{dp.\mathrm{And}Y}=E_{\mathrm{with\; a}m.\mathrm{And}3}(1+\frac{R_1}{R_2})=2E_{\mathrm{with\; a}m.\mathrm{And}3}\text{(12)}$$

the zero drift is almost 2 times the zero drift of the claimed device.

The decrease in K_CH(formula 6) due to K_Assn<<1 is explained by the differential properties of the input key and an additional differential cascade input converters "voltage-current" (15, 18) of the input precision of the Converter (1).

Thus, the influence of techno is logicheskih to manufacturing errors of the resistors Θ _Riapplies only to the differential gain (4) and practically does not affect the gear ratio common-mode signal (6) and the zero drift (9), which is also seen on Fig - Fig (PS 2) and Fig - Fig (PS 6).

The accuracy of the implementation of the differential gear ratio is determined by the influence of the static amplification factor (µ):

$$S_{\mu }^{Kd}=1-\frac{\mu }{\mu +K_d}=\frac{K_d}{\mu +K_d/2}\approx \frac{K_d}{\mu },\text{(12)}$$

$$\frac{\Delta K_d}{K_d}=S_{\mu }^{K_d}.\frac{\Delta \mu }{\mu },\text{(13)}$$

$$K_{d.\max }=\frac{\Delta K_d/K_d\cdot \mu }{\Delta \mu /\mu },\text{(14)}$$

where Δµ/µ - accuracy static gain is determined by the error process, ΔK_d/K_d- accuracy differential gain, µ is the static gain, the increase of which, with the help of effective technical solutions that can reduce the error differential gain.

Consider the work of Yiwu 6.

The work of the instrumental amplifier 6 is different from that of the instrumental amplifier 2, so that in its structure between the outputs of the input precision of the Converter 1 and the inputs of the active accumulator (12) is enabled filters low frequencies (35, 36) for each of the channels of amplification. This implementation of the instrumental amplifier allows you to minimize the error EMF offset lowpass filter made in the final result, due to the implementation of high common-mode rejection signal in the input stages of the fourth (27) Converter "voltage-current" active adder (12) (figure 5), providing for its suppression.

Depending on the selected values of the capacitor in an RC circuit filters the lower frequent the t (35, 36), is determined by the cutoff frequency of the bandwidth of the frequency characteristics of the instrumental amplifier. So each of the low-pass filters (35, 36) 6, implements the transfer function

$$F_F(p)=\frac{a_0}{p^3+p^2{a}_2+p{a}_1+a_0},\text{(15)}$$

factors which

$$\begin{array}{l}{a}_2=\frac{g_{41}+g_{42}}{C_{45}}+\frac{g_{42}+g_{43}}{C_{46}},{\text{a}}_{\text{1}}=\frac{g_{41}(g_{42}+g_{43})+g_{42}{g}_{43}}{C_{45}{C}_{46}}+\frac{g_{42}{g}_{43}}{C_{45}{C}_{46}},\\ a_0=\frac{g_{41}{g}_{42}{g}_{43}}{C_{45}{C}_{46}{C}_{47}},{\text{g}}_{\text{41}}=\raisebox{1ex}{$1$}\!\left/ \!\raisebox{-1ex}{$R_{41}$}\right.,g_{42}=\raisebox{1ex}{$1$}\!\left/ \!\raisebox{-1ex}{$R_{42}$}\right.g_{43}=\raisebox{1ex}{$1$}\!\left/ \!\raisebox{-1ex}{$R_{43},$}\right.\text{(16)}\end{array}$$

where C₄₅With₄₆With₄₇the capacitor in an RC circuit low-pass filters (35, 36), R₄₁, R₄₂, R₄₃the resistors in the RC-circuit low-pass filters (35, 36), low (≤1) elemental sensitivity to the instability of the parameters of resistors and capacitors. For small-scale non-uniformity of the amplitude-frequency characteristics (AFC) in bandwidth for a rational choice of the approximation function q of the pole is small, so you can use additional pairs of the electrical conditions:

$$R_{41}=R_{42}=R_{43};{\text{C}}_{\text{45}},=C_{46}=C_{47};{\text{C}}_{\text{45}}=hC.\text{(17)}$$

Then

$$a_2=\frac{2(h+1)}{RCh},{\text{a}}_{\text{1}}=\frac{4}{R^2{C}^{2}h},{\text{a}}_{\text{0}}=\frac{1}{R^3{C}^{3}h},\text{(18)}$$

with correspondence relations denominations of the same elements corresponds to the structure of the ladder filter.

Thus, the proposed instrumental amplifier 2 and 6 differs from the prototype and analogs, which is characterized by lower power consumption and lower cost by reducing kolichestvobyudzhetnykh components and requirements for their accuracy, higher (the highest achievable) common-mode rejection signal, weakly dependent on the errors of the resistive elements in the circuit, thus avoiding costly precision laser configure these resistors.

Also offer instrumental amplifier is characterized by a more efficient use of amplitude characteristics of the outputs (5) and (6) input precision transducer (1) and low voltage zero drift instrumental amplifier having a low dependence on the errors of the non-identical resistive elements in the circuit, due to the implementation of high attenuation common-mode component of the input signal in the input cascade input converters "voltage-current" (15, 18) input precision transducer (1) (2, 6).

Data theoretical conclusions are confirmed by figure 10 graphs - Fig

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15. Patent US 00004206416

16. Patent US 00003453554

1. Instrumental amplifier, containing the s input precision Converter (1) first (2) and second (3) input voltage, associated with the common power bus (4), first (5) and second (6) outputs the input precision of the Converter (1), the first (7) and second (8) inputs of the device associated with the first (2) and second (3) sources of input voltages, the first (9), second (10) and third (11) of the feedback resistors, the active accumulator (12) inverting (13) and reinvestiruet (14) inputs, the output device (15)connected to the output of the active accumulator (12), and first (5) output input precision transducer (1) is connected with the inverting input (13) of the active accumulator (12), second (6) output input precision transducer (1) is associated with reinvestiruet input (14) of the active accumulator (12), characterized in that the input precision Converter (1) includes first (15) Converter "voltage-current", the inverting input of which is connected with the first (7) input device, and a non-inverting input is connected with the second (8) the input of the first (16) the current output of the first (15) Converter "voltage-current" is connected with the first (17) current output of the second (18) Converter "voltage-current" and is connected to the not inverting current input of the first (19) the output of the Converter "current-voltage" and to the inverting current input of the second (20) output Converter "current-voltage", the second current output (21) of the first (15) Converter "voltage-current" connect the n second (22) a current output of the second (18) of the inverter voltage current, and is connected to the inverting current input of the first (19) the output of the Converter "current-voltage" and not inverting the input of the second current (20) the output of the Converter "current-voltage", and the signal on the first (16) the current output of the first (15) Converter "voltage-current" out-of-phase signal on the second (21) the current output of the first (15) Converter "voltage-current", and the signal on the first (17) the current output of the second (18) Converter "voltage-current" out-of-phase signal on the second (22) the current output of the second (18) of the inverter, the voltage-current and common-mode signals on the first (16) the current output of the first 15) Converter "voltage-current", the output (23) of the first (19) the output of the Converter "current-voltage" is connected with the first (5) the output precision of the Converter (1), and is also connected with the inverting input of the second (18) Converter "voltage-current" through the second (10) feedback resistor, and the inverting input of the second (18) Converter "voltage-current" is connected to the common bus power supply (4) through an optional feedback resistor (24), the output (25) of the second (20) the output of the Converter "current-voltage" is connected with the second (6) the output precision of the Converter (1), and is also associated with reinvestiruet input of the second (18) Converter "voltage-current" through the first (9) feedback resistor, and the non-inverting input of the second (18) Converter "voltage-current" is connected to the common bus power supply (4) che the ez third (11) of the feedback resistor.

2. Instrumental amplifier according to claim 1, characterized in that the active accumulator (12) includes a third (26) Converter "voltage-current", inverting input connected to the output device (15), and the non-inverting input connected with a common bus power supply (4), fourth (27) Converter "voltage-current", the inverting input of which is connected to the inverting input (13) of the active accumulator (12), the non-inverting input connected to the not inverting input (14) of the active accumulator (12), the first (28) the current output of the third 26) Converter "voltage-current" is connected with the first (29) current output of the fourth (27) Converter "voltage-current" and is connected to the not inverting current input of the third (30) of the output Converter "current-voltage", the second (31) the current output of the third (26) of the inverter "voltage-current" is connected with the second (32) a current output of the fourth (27) Converter "voltage-current" and is connected to the inverting current input of the third (30) of the output Converter "current-voltage", and the signal on the first (28) the current output of the third (26) of the inverter "voltage-current" out-of-phase signal on the second (31) the current output of the third (26) of the inverter "voltage-current", and the signal on the first (29) the current output of the fourth (27) Converter "voltage-current" out-of-phase signal on the second (32)the current output of the fourth (27) Converter "voltage-current" and the common mode signal on the first (28) the current output of the third (26) of the inverter "voltage-current".

3. Instrumental amplifier according to claim 1, characterized in that the first (5) output input precision transducer (1) is connected with the inverting input (13) of the active accumulator (12) through the first (35) the lowpass filter, and the second (6) output input precision transducer (1) is associated with reinvestiruet input (14) of the active accumulator (12) through the second (36) low pass filter.

4. Instrumental amplifier according to claim 1, characterized in that the first (5) and second (6) outputs the input precision of the Converter (1) is associated with a respective inverting (13) and reinvestiruet (14) the active inputs of the adder (12) via a differential input and differential output filter frequencies (48).