Amplifier

 

(57) Abstract:

Usage: for amplification of the signals with high dynamic accuracy. The inventive amplifier, built on two operational amplifiers (high-precision and high-speed) introduces an additional resistor, and the ratio between the resistors is selected so that the total amplitude-frequency characteristic of the amplifier has a slope of - 20 dB/Dec. In the dynamic properties of the amplifier are determined by the high-speed operational amplifier and the accuracy specifications precision operational amplifier. 1 Il.

The invention relates to electronic devices and can be used to amplify signals with high dynamic accuracy.

Known amplifier containing the first and second operational amplifiers (OA), covered by independent negative feedbacks and connected in series [1] Its disadvantage is the low dynamic accuracy. Known amplifiers closest to the technical essence is the device described in [2]. This amplifier is composed of the first OS and the second OS, the first and second resistors, and the first resi is the dominant input and output of the second OS, non-inverting input of the first OS is connected to a shared bus, non-inverting input of the second OS is connected to the output of the first OS, the output of the second OS is the output of the amplifier.

The objective of the invention is to improve the dynamic accuracy. The problem is solved in that the amplifier consisting of the first OS and the second OS, the first and second resistors, the first resistor connected between the input of the amplifier and the inverting input of the first OS, a second resistor connected between the inverting input and output of the second OS, the non-inverting input of the first OS is connected to a shared bus, non-inverting input of the second OS is connected to the output of the first OS, the output of the second OS is the output of the amplifier introduces an additional resistor that is connected between the inverting inputs of the first and second OS, and the ratio of the resistors is chosen equal to (Rd+ R2)/R1K, where R1, R2, Rdrespectively the first, second and additional resistors, f1and f2the unity gain frequency of the first and second OS.

The essence of the proposal is illustrated by a drawing, which shows the amplifier circuit, which contains: 1 first resistor (R1), 2 OS, 3 - additional resistor connected between the input of the amplifier and the inverting input of the first OS, a second resistor connected between the inverting input and output of the second OS, the non-inverting input of the first OS is connected to a shared bus, non-inverting input of the second OS is connected to the output of the first OS, the output of the second OS is the output of the amplifier introduces an additional resistor that is connected between the inverting inputs of the first and second OS.

The amplifier circuit operates as follows: first the OS, which determines the bias voltage and temperature drift of the bias voltage of the entire amplifier is implemented on a precise OS and usually has a low performance. The second OS, which has virtually no effect on the bias voltage and temperature drift, can be implemented on the basis of a fast OS. When it arrives at the amplifier input surge in the beginning because of the lag caused by the poor performance of the first OS, the output voltage is determined by the second OS. Then, as the output voltage rise, increasingly the first OS and eventually DC only the first OS. To explain the positive effect of present OS of the linear inertia of the links of the first order. Their transmission characteristics can be made>the gains of the first and second OS on direct current, respectively,1and2their time constants. Taking into account inequalities TO1>> 1 and K2>> 1, the transfer characteristic of the amplifier can be represented as:

(2)

where K01 + (Rd+ R3)/R1, 1 + R2/R1, (3) C given that

t1/K1= 1/2f1and2/K2= 1/2f2,

where f1and f2frequency unity gain, respectively, the first and second operational amplifiers, the transfer characteristic of the amplifier can be represented in the form:

(4)

the denominator of the right side can be represented as:

(5)

where0the degree of acceleration and circular resonant frequency, and

(6)

(7)

Imagine the formula (2)

(8)

where

(9)

(10)

(11)

From(6), (7), (9) (11) it is seen that if the selected OU and OU the values of f1and f2known, and the value TO0specified, then the value of f0entirely defined, and T1T2T3depend on a, i.e. on the ratio Rd/R1.

To declare the schema of interest is the value a defined by the formula:

(12)

and

There is some boundary value TO a0determined by the formula

(13)

When K < Kgis there

(14)

and treatment (8)

Ku(p) (K0- 1)/(1 + pT2) (15)

where T2determined (10).

When K > Kg< / BR>
(16)

and the formula (8) becomes

TOy(b) (1)/(1 + RT1) (17)

where T1is determined by (9). Transfer characteristics (15) and (17) corresponds to the asymptotic LATCH with a slope of -20 dB/Dec.

From the above it is evident that when the conditions of the transfer function becomes close to the transfer characteristic of the inertial element of the first order, which is smaller than the reference time setting to the desired accuracy.

As the first OS can be used chip type KDA, as well as a second chip type COA. Resistors can be taken of the type S2-29V.

Sources of information

1. A. G. Alexenko, E. A. Particularly, G. I. Starodub. The use of precision analog circuits. M. Chapman and hall, 1985, S. 22, Fig. 1.16.

2. Amplifiers with parallel channels.// Instruments and control elements and vychislitelnyi, first and second resistors, and the first output of the first resistor is the input of the amplifier and a second output connected to the inverting input of the first operational amplifier, a noninverting input connected to a shared bus, and the output from reinvestiruet input of the second operational amplifier whose output is the output of the amplifier and via a second resistor connected to the inverting input of the second operational amplifier, characterized in that it introduced an additional resistor connected between the inverting inputs of the first and second operational amplifiers, and the ratio of the resistors is selected to be

(Rd+ R2) /R1K1;

< / BR>
where R1, R2, Rdfirst and second additional resistor, respectively;

f1f2the unity gain frequency of the first and second operational amplifiers.

 

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