SU1642586A1 - Da converter - Google Patents

Abstract

The invention relates to automation and computing and can be used in precision analog-digital and digital-analog systems. The purpose of the invention is to improve the accuracy of the conversion by stabilizing the slope of the conversion characteristic. The digital-to-tax converter contains the first 1 and second 2 code-to-current converters, the first 3 and second 4 operational amplifiers, the first 5 and second 6 feedback elements. A positive effect is achieved by making the second converter 2 functional, the output current 2 of which is associated with the value of the NBx code being converted by the dependence 12 IHOM VI - (LHD / LHhmax.) 2 where the current ratio at the output of the converter 1 at the maximum value of H. Max. input code. 1 hp f-ly, 2 ill.

Description

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The invention relates to automation and computing and can be used in precision systems of analog-digital and digital-analog conversion.

The purpose of the invention is to improve the accuracy of the conversion by stabilizing the slope of the conversion characteristic.

FIG. 1 shows a functional diagram of a digital-to-analog converter; 2 shows the implementation of a functional code-to-current converter.

The digital-to-analog converter (Fig. 1) contains the first 1 and second 2 code-to-current converters, the first 3 and second 4 operational amplifiers, the first 5 and second 6 feedback elements, made respectively on the first and second resistors having thermal coupling.

The second code-to-current converter 2 (Fig. 2) is made functional in the form of a binary-code converter into a positional, source-8 reference voltage, (2-1) discharge resistors 9.1-En and 2-1 discharge keys 10.1 -10.p, where k is the width of the code to be converted.

Digital to analog converter (figure 1) works as follows.

The converted NBx code goes to the control inputs of the first code-to-current converter, the output current of which is related to the value of the code being converted by the expression

And UoRsKB nom.in./MVx.max,

where Uo and RSKB, respectively, are the voltage of the source of the reference voltage and the equivalent resistance of the code-optic divider, which are part of the first converter 1 of the code into current;

IHOM is the value of the output current of the first converter of 1 code into current at the maximum value of Bin.max of the converted code;

Nsx 2 3 | 2 1, N in. Max 2k - 1,

I 1 ai 0 or 1.

The output current ft of the first converter 1 of the code into the current is converted by the first operational amplifier 3 with a resistor 5 in the feedback circuit to the output voltage of the 11th digital-to-analog converter equal to

 lnoMRINex / Nex-MaKc.

The output current 2 of the second converter 2 code into current is determined by the functional dependence

IfVWoM-lT

Current 12 flows through the second resistor 6 with resistance R2, which is connected to the negative feedback circuit of the second operational amplifier 4. 5 Summarnnom power allocated to

resistors 5 and b, is equal to РЈ Pi + P2

- 112R1 + l22R2 (R1 - R2) (lHoMNBx / NBx.MaKc.) 2+

+ IHOM R2 and while ensuring equality

0

five

0

five

0

R1 R2 R we get P Ј IHOM R.

The independence of the total power due to the thermal connection between the resistors 5 and 6 causes the resistance of the resistor 5 to remain constant and, consequently, the stability of the slope of the conversion characteristics of the digital-to-analog converter.

The required functional dependence of the current 2 on the value of the code being converted is ensured by the appropriate choice of the resistances of the discharge resistors 9.1-E and the algorithm of the operation of the second (Functional) converter 2 of the code into current (Fig. 2). The input code of the binary type, which is fed to the control inputs of the second converter 2 of the code into current, is converted by means of the converter 7 of the binary code into the positional one. At a certain value of the input code NBxj, a signal is generated at the corresponding j-th output of the converter 7 with a loss of log.1, which closes the j-th bit 10.J. Under the influence of the reference signal of the source 8 of the reference voltage through the j-th discharge resistor 9.J with resistance R9j a current l2j Uo / R9j flows, which is the output current of the functional converter 2 codes into current, Resistance j-ro of the discharge resistor 9.J is selected according to the expression

0

R9.J R9.1 / Vl - (j -1) V (2k -1) 2,

where 2,3 (2k-1);

R9.1 is the resistance of the first discharge resistor, R9.1 UO / IHOM.

Claims (2)

Claim 1. A digital-to-analog converter containing first and second code-to-current converters whose outputs are connected. with inverting inputs, respectively, of the first and second operational amplifiers, the non-inverting inputs of which are connected to the zero potential bus, and the outputs, respectively, through the first and second elements of the communication, made respectively as the first and second resistors with a thermal connection between them, are connected respectively with their inverting inputs, output first The operational amplifier is the output bus; the control inputs of the first code-to-current converter are combined with the corresponding control inputs of the second code-to-current converter; and are input bus, characterized in that, in order to increase the conversion accuracy by stabilizing the slope of the conversion characteristic, the second the code-to-current converter is made functional, wherein the output current of the functional converter and the code to be converted are in the following relationship; l2 IHOM Vl -Nix / (2k-1) 2, where z is the output current of the functional converter; k NBX z, ai 2 - the value of the converted code; ai 0 or 1 is the i-ro value of the bit ratio of the code being converted; k is the width of the code to be converted, IHOM is the output current value of the first code-to-current converter at ai 1 for all, 2k. 2. The converter according to claim 1, about tl and h a tout and with the fact that the second converter 0 five 0 The code into current is made in the form of a voltage source, a binary code-to-position converter, 2k-1 bit resistors and 2 -1 bit switches, the control inputs of which are connected to the corresponding outputs of the binary code to position transducer, whose inputs are corresponding the control inputs of the second code-to-current converter, the first and second outputs of the voltage source are connected respectively to the zero potential bus and to the first terminals 2k-1 of the discharge resistors, the second terminals of which connected to the inputs of the corresponding bit switches, the output of the first bit switch is combined with the outputs of the remaining 2-2 bit switches and is the output of the second code-to-current converter, while the resistance of the j-ro bit resistor, except the first, is determined according to with expression 25 Rj Rl / Vr- (J-1 f / (2k-lf, where Ri UO / IHOM is the resistance of the first discharge resistor; Do is the voltage source of the reference voltage; 1 2, 3 (2k-1). ±