SU1667253A1 - Bipolar number-to-voltage converter - Google Patents

Abstract

The invention relates to automation and computing and can be used to build code converters into a bipolar analog signal with an arbitrary slope. The purpose of the invention is to expand the field of application by expanding the range of variation of the code conversion slope into an analog signal. The bipolar code-to-voltage converter contains an R-2R type code-controlled resistive matrix 1, an operational amplifier 2, the first 3 and second 4 switches, and four resistors 5 to 8. A positive effect was achieved by introducing the second switch 4 and the fourth resistor 8, which allowed to independently set the slope of the transformation for both positive and negative values of the code being converted. 1 il.

Description

The invention relates to automation and computer technology and can be used to build code converters in a bipolar signal with an arbitrary value of the conversion slope.

The purpose of the invention is the expansion of the scope by providing an extension of the range of variation of the steepness of the conversion of the code into an analog signal.

The drawing shows a functional diagram of a bipolar code-to-voltage converter.

The bipolar code-to-voltage converter contains a code-controlled resistive matrix 1 of type R - 2R, an operational amplifier 2, the first 3 and second 4 switches and four resistors 5 ~ 8.

The bipolar code-to-voltage converter operates as follows.

On the inverter input receives convertible code Ν _Β χ. whose sign is determined by the value of a sign discharge. With a positive value of the code Ν _Β χ (o = 0), the output voltage of the code-controlled resistive matrix 1 of type R 2R through the first switch 3 is fed to the non-inverting input of the operational amplifier (OA) 2. This voltage is scaled using the first resistor 7 (taking into account the output resistance of the code the resistive matrix 1). The transfer coefficient of the op-amp 2 is set in this case with the help of scaling resistors 5 and 6. The connection node of which, using the second switch 4, is connected to the non-inverting input of the op-amp 2. In this case, the output signal of the bipolar converter is determined by the expression

and - ^R4 - ~ / ^s R + R4 ( 1 R2> Ou nbx I -y K Ν _Β χ - θ 2 ^P

p L R1 where K + = - (1 + · ——) is the transmission coefficient of the op-amp 2 in the positive code conversion mode;

Uo. R are the values of the reference voltage and the output resistance of the code-controlled resistive matrix 1, respectively;

Ν _Β χ.η value and bit depth of the converted code, respectively:

R1, R2. R4 - resistance values of resistors 5, 6 and 7, respectively.

When the negative code 5 N _B x (<z- 1) is received at the input of the bipolar converter, the first 3 and second 4 switches are switched. As a result, the output signal of the code-controlled matrix 1 is fed to the inverting input of the op-amp 2. In the feedback circuit 10 of which the resistor 8 is turned on. And the non-inverting input through the resistor 7 is connected to the zero potential bus. In this case, the voltage at the output of the bipolar converter is determined by the expression

II - R3 Uo _c . _ and _YOU х р— Νβχ 20 = ' ^to Nbx R3 where К - - - transmission coefficient of the op-amp 2

K in negative code conversion mode:

R3 - resistance of the resistor 8.

From the obtained expressions it follows that the values of the coefficients Kr and K can be selected independently of each other, while the steepness of the conversion of the positive and negative codes will be different. To ensure the linearity of the conversion characteristics in the range from the maximum negative to the maximum positive code values, it is necessary to ensure the equality Kg = K- = K. The latter is performed while satisfying the following relations between the resistances of the resistors:

1 / R ‘1 / R3 = 1 / R4 and 1 / R + 1 / R4 = = 1 / R1 + 1 / R2.

⁴ 5 Thus, given the known output resistance R of the code-controlled matrix 1, the K value of the gain of the op-amp 2, calculate the resistance values of all resistors 5 8.

Claims (1)

Claim A bipolar code-to-voltage converter containing three scaling55 elements, each of which is made in the form of a resistor, a code-controlled resistive matrix of type R - 2R. the control inputs of which are the input bus of the converted code, the first switch, the control input of which is the input bus of the sign discharge, the operational amplifier, the non-inverting input of which is connected to the first output of the first resistor, the output of the operational amplifier is the output bus and connected through the second resistor to the first output of the third resistor characterized in that. that, in order to expand the scope by providing an extension of the range of variation of the steepness of the transformation, a fourth scaling element is introduced into it. made in the form of a fourth resistor. and a second switch, the control input of which is combined with the control input of the first switch, the information input of which is connected to the output of a code-controlled resistive matrix of type R - 2R, and the first and second outputs are connected respectively to the inverting and non-inverting inputs of the operational amplifier, the output of which through the fourth resistor is connected to the first output of the second switch. the information input of which is combined with the inverting input of the operational amplifier, the second terminals of the first and third resistors are connected to the zero potential bus, the first terminal of the third resistor is connected to the second output of the second switch.