SU1566464A1 - Direct voltage amplifier - Google Patents

Abstract

A DC voltage amplifier containing a serially connected modulator with a differential input, a first AC voltage amplifier, a band-pass filter, a second AC voltage amplifier, a demodulator, an integrator, the output of which is connected to the second modulator input with a differential circuit. input, as well as a control generator, the output of which is connected to the control inputs of a modulator with a differential input and a demodulator, characterized in that, in order to improve accuracy by increasing ehozaschischennosti between the first amplifier output AC voltage and the second input of the modulator differential input administered serially connected optional demodulator, an additional bandpass filter, the inverter voltage - current, said control generator output is connected to the control input of the additional demodulator.

Description

The invention relates to a measurement technique, in particular to an M-DM amplifier of DC voltage to amplify small DC voltages against the background of strong interference in the form of alternating voltages.

A M-DM amplifier is known, comprising a modulator, an AC signal amplifier and a demodulator in series; as well as the feedback circuit of the PM-DM amplifier has insufficient accuracy due to the lack of noise immunity.

The closest to the technical essence of the invention is a DC amplifier, with

holding a serially connected modulator with a differential input, a first AC voltage amplifier, a bandpass filter, a second AC voltage amplifier, a demodulator, an integrator whose output is connected via a feedback circuit to the second input of the modulator with a differential input, and a control generator The output of which is connected to the control inputs of a modulator with a differential input and a demodulator 2J.

The known DC voltage amplifier does not have sufficiently high accuracy due to the low level of noise immunity.

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The purpose of the invention is to improve accuracy by improving noise immunity.

The goal is achieved by the fact that a DC amplifier containing a series-connected modulator with a differential input, a first AC amplifier, a band-pass filter, a second AC amplifier, and a demodulator, an integrator, whose output is through a reverse circuit. connection is connected to the second input of a modulator with a differential input, as well as a control generator, the output of which is connected to the control inputs of a modulator with a differential input and a demodulator, between the output of the first An alternating voltage cell and a second input of a modulator with a differential input are connected in series an additional demodulator, an additional band-pass filter, and a voltage converter is a current, with the output of the control generator connected to the control input of the additional demodulator.

FIG. 1 shows a structural electrical circuit of a dc amplifier; 2 and 3 are time diagrams of stresses in

separate points of the scheme.

DC Power Amplifier

contains modulator 1 with differential input — with first 2 and second 3 inputs, first alternating voltage amplifier 4, band-pass filter 5, alternating voltage second amplifier 6, demodulator 7, integrator 8, feedback circuit 9, control generator 10 , additional demodulator 11, additional band-pass filter 12, voltage converter 13 — current.

The constant voltage amplifier operates as follows.

The first input 2 is supplied with the sum of the amplified DC voltage (Fig. 2a, 1) and the noise (Fig. 2a, II) is usually a sinusoid with a frequency of 50 Hz. Due to the fact that the amplification of the external circuit containing the feedback circuit 9 is very large, at the second input 3 we also have a constant voltage (Fig. 26, II), which practically coincides in value with the voltage (Fig. 26, II ). At a constant voltage (Fig. 26, II), the overlaps

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with

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An alternating voltage (Fig. 26, I) created by an additional CBHSH reverse circuit (an additional demodulator 11, an additional band-pass filter 12, a voltage converter 13 - current) approximately equal to the voltage (Fig. 2a, I) .

Modulator 1 modulates the difference of voltages applied to the first 2 and second 3 inputs, multiplying this difference with a voltage (Fig. 2b) of type (square wave supplied from the output of the generator 10 to the control input of the modulator 1.

The voltage (Fig. 2d) at the input of the first amplifier 4 contains almost no component with a modulation frequency (due to the equality of the voltages, Figs. 2a, II, and 6.11), the result of the modulation of the voltage difference of Fig. 2 being predominant. 2a, 1 and 6.1,

Broadband voltage amplification occurs in the first amplifier 4 (Fig. 2d). Further conversion of this voltage occurs in subsequent blocks similarly to: a constant voltage is observed at the output of the dc amplifier, which is K times the input voltage (Fig. 2a, II) if the feedback circuit 9 is resistive divider with a division factor of 1 / K.

Suppose that the input voltage of the bandpass filter 5, also entering the additional demodulator 11, is the sum of two components: the voltage (fig. 2d) as a result of modulation and amplification of the voltage difference (fig. 2a, i and b, i) and voltages (Fig. 3a) with the modulation frequency caused by the zero drift of the modulator 1 and inaccurate coincidence of the voltages (Figures 2a, II and b, II).

The voltage (Fig. 2d) at its considerable amplitude is the cause of possible overloads in the amplification path.

In view of the fact that the additional demodulator 11 is a linear circuit, we can consider the further transformation of voltages (fig.2d and Za) separately. In the additional demodulator 11, the voltage (FIG. 2d) is multiplied with the voltage (FIG. 2c) supplied from the output of the generator 10 to the CVDF.

Control Additional Demodulator 1 I. As a result, a voltage is applied to the input of the additional bandpass filter 12 (FIG. 3b), which is slightly different in shape (usually a sine wave) from the interference voltage (FIG. 2a, I) acting on the first input 2. Similarly to the result of voltage conversion (FIG. In the additional demodulator 11, there is a constant voltage (Fig. 3g). At the input of the additional band-pass filter 12, a sum of voltages is thus observed (Fig. 3b and c).

The additional band-pass filter 12 performs three functions: it prevents the penetration of a direct voltage (FIG. 3) to the input of the voltage converter 13 —current, corrects the frequency response along the direct gain circuit (blocks 1, 4–8) and feedback (blocks 11-13) in order to ensure the stability of the circuit and achieve maximum noise immunity of the entire amplifier and suppress parasitic pulsation with the modulation frequency at the output of the additional demodulator 11. At the input of the converter 13, the voltage - current is therefore observed variable (sinusoidal) voltage (Fig. 3g) without a constant component in general with amplitude and phase different from the corresponding voltage parameters at the input of the additional bandpass filter 12.

The purpose of applying voltage converter 13 is current to provide summation of signals from the outputs of feedback circuit 9 and additional

band pass filter 12 at the second input 3 of the modulator 1 without degrading the gain accuracy of the entire dc amplifier. The feedback circuit 9 has an exact output impedance determined by precision resistors and therefore the connection of low-resistance circuits parallel to the output of the feedback circuit 9 is unacceptable.

The voltage (Fig. 26, I) at the second input 3 of the modulator 1 is created by converting the voltage (Fig. 2d) into a proportional current into a converter.

voltage 13 - current (has a high output resistance). and by further passing this worm current, the output resistance of the feedback circuit 9,

Thus, in the proposed amplifier, the accuracy is improved by increasing noise immunity.

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Claims (1)

A DC voltage amplifier containing a series-connected modulator with a differential input, a first AC amplifier, a bandpass filter, a second AC amplifier, a demodulator, an integrator, the output of which is connected through a feedback circuit to the second input of a modulator with a differential input, and a control generator, an output which is connected to the control inputs of a modulator with a differential input and a demodulator, characterized in that, in order to improve accuracy by increasing mehozaschischennosti, between the output AC voltage of the first amplifier and the second input to the differential modulator WMOs house administered serially connected optional demodulator, an additional bandpass filter, the inverter voltage - current, wherein the control output of the generator is connected to the additional control input 'Nogo demodulator.