SU1576870A1 - Converter of parameters of complex resistances to voltage - Google Patents

Abstract

The invention relates to information-measuring technology and automation and can be used in the conversion, measurement and tolerance control parameters of the elements of complex electrical circuits, as well as in the construction of high-frequency crucial amplifiers. The purpose of the invention — improving the accuracy of the conversion — is achieved by creating a stable amplifier with an overall deep negative feedback and a large intrinsic gain in a wide frequency range. The device contains an impedance amplifier 1, a tunable resonant amplifier 2, an exemplary resistor 3 and an impedance 4 and is a multi-stage tunable selective amplifier covered by a common negative feedback. A feature of the device is the lack of dynamic error. 2 Il.

Description

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The invention relates to information-measuring technology and automation and can be used in the conversion, measurement and tolerance control parameters of the elements of complex electrical circuits, as well as in the construction of high-precision decision amplifiers.

The aim of the invention is to improve the accuracy of the impedance-to-voltage converter by creating a stable amplifier with an overall deep negative feedback and a large intrinsic gain in a wide frequency range. An increase in the noise immunity of the device is achieved.

Fig. 1 shows a block diagram of a converter of the parameters of complex resistance to voltage; figure 2 - the same option.

The converter contains impedance amplifier 1, tunable resonant amplifier 2, exemplary resistor 3 and impedance 4, which is connected to the input of impedance amplifier 1, the output of which is connected to the input of tunable resonant amplifier 2. Exemplary resistor 3 is connected to the common negative feedback between the input impedance amplifier 1 and the output of a tunable resonant amplifier 2. Resistance amplifier 1 is an amplifier whose input value is k, and the output - voltage, size-ness its transmission factor is expressed in ohms. In this case, the amplifier has low input and output impedances. For example, it can be performed on the basis of a transistor stage with a common base or using a conventional operational amplifier (Fig. 2). In particular, the converter can contain standard operational amplifiers 5-7, resistors 8-10, inductor coils 11 and 12, and variable capacitors 13 and 14. A tunable resonant amplifier can be assembled on operational amplifiers 6 and 7 (including non-inverting) negative feedbacks of which include parallel oscillatory circuits on inductor coils 11 and 12 and paired variable capacitors 1 3

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and 14. The impedance amplifier is assembled at the operational amplifier 5, the low input impedance of which is provided by deep negative feedback using a resistor 8.

The Converter operates as follows.

By adjusting the variable capacitors 13 and 14, calibrated in units of frequency, the resonant amplifier 2 is tuned to the frequency of the input signal. The input voltage is applied to the converted impedance 4. At the same time, the current flowing through the impedance 4 is converted / (with a transfer coefficient equal to the value of the 8J resistor using the resistance amplifier 1 to a voltage that is greatly amplified by the resonant amplifier 2. The circuit is negative feedback (resistor 3) stabilizes the operation of the converter and ensures high accuracy of the conversion at a given frequency. Consequently, the output voltage of the converter is proportional to impedance 4.

The real transfer coefficient of the converter K is

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thirty

five

0

five

TO

where u

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one

in

ZjV + Z "

RSK R

R.

YOU

ex

rn and R8 - K the output voltage of the converter;

converter input voltage;

the complex resistance of the studied two-terminal;

Resistances of resistors -3 and 8, respectively; own coefficient of amplifier 2 at the resonant frequency.

Since the ideal transfer coefficient of the converter is of the form Kn R, / R4, the relative error of the transfer coefficient is equal to

f- -100%.

(ABOUT

8-p

Let's compare the static error of the proposed converter with the same error of the commercially available operational amplifier (OU).

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It is natural that his error

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(2)

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-oyf5 04 - own coefficient

reinforcement op amp; | 3 is the feedback coefficient. reading expressions (1) and (2), we get

& e4aj ji-.L ,. (3)

R8KtK

 Q (J

For simplicity, we introduce the following relations:

KZ

0.1Z

h

four

- kog

(4) (5) (6)

In relation (5), the factor of 0.1 means that amplifier 1 can be a resistance amplifier only with deep negative feedback in amplifier 5 (Fig. 2). Expression (6) is valid only at the resonant frequency. Since amplifiers 6 and 7 practically have infinitely large resistance in the circuit

feedback, their total coefficient

the gain is equal to l (4), (5) and (6) in

Ko "j- (3),

Substitute

WITH

.0 pts

(7)

From the expression 7) it follows that the static error of the proposed

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Converter less error

base device in 0, fK

° s

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For example, when using an OS chip (K544UD2) at a frequency of 10 kHz, the error of the proposed converter is 300 times less than the error of the base object.

The essential feature of the proposed converter is the absence of dynamic error. The proposed converter retains its stability, since the phase balance condition is not fulfilled at the resonant frequency, while the amplitude balance condition is not fulfilled at other frequencies.

Claims (1)

Invention Formula A converter of the impedance parameters to a voltage containing a tunable resonant amplifier, characterized in that, in order to increase the conversion accuracy, a resistance amplifier and an exemplary resistor are inserted in it, the complex resistance connected to the input of the resistance amplifier, the output of which is connected to the input of a tunable a resonant amplifier, and an exemplary resistor is connected to the common negative feedback circuit between the tunable resonant amplifier output and the input ohm impedance of the amplifier. Compiled by V. Bobrov Editor I. Gorn Tehred M. Didyk Order 1845 Circulation 558 VNIIPI State Committee for Inventions and Discoveries at the State Committee on Science and Technology (CST) C (JCP 113035, Moscow, Zh-35, 4/5 Raushsk Nab. Production and Publishing Combine Patent, Uzhgorod, st. Gagarin, 101 Phage. 2 Proofreader E. Lonchakova Subscription