JPH01290316A - D/a converter - Google Patents

Abstract

PURPOSE:To improve the linearity of a digital analog converter by using an input conversion table correcting the nonlinearity of the digital analog converter so as to convert the input digital signal and input the result to the said converter. CONSTITUTION:An input conversion table 2 giving an input to correct the nonlinearity of the digital analog converter 4 is generated. The input digital signal 1 is converted into a converted digital signal input 3 by the input conversion table 2. The converted digital signal input 3 is inputted to the digital analog converter 4. The digital analog converter 4 outputs a linear analog output signal. Through the constitution above, the linearity of the digital analog converter is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a D/A converter, and particularly to the linearity of its characteristics.

[Prior Art] There are various types of D/A converters, all of which are well known in the past. It was difficult to obtain linearity of input/output characteristics.

Figure 3 is a characteristic diagram showing the input/output characteristics of a conventional D/A converter, where the horizontal axis shows the digital signal input, the vertical axis shows the analog signal output, and the straight line indicated by Av is the ideal input/output characteristic. However, the actual input/output characteristics are nonlinear characteristics shown by Ar.

[Problem to be solved by the invention] No matter what type of conventional D/A converter is, the third
It has nonlinear characteristics as shown in the figure, but the so-called ladder type R-2RD/A converter is particularly susceptible to nonlinear characteristics, and to improve this, output buffers and It was adjusted by changing the feedback resistance value.

In this method, it is difficult to achieve linearity because the buffer size, the feedback resistance value, and the R-2R resistance of the input stage influence each other. Furthermore, depending on how the feedback resistor is determined, the buffer size becomes large, leading to a problem that the chip size becomes large. It is an object of the present invention to solve the above-mentioned problems in conventional devices and to provide a D/A converter having linear characteristics by adding a simple circuit.

[Means for Solving the Problems] In the present invention, an input conversion table is created that provides an input that corrects the nonlinearity of the D/A converter, and after converting the input digital signal using this table, the D/A converter I decided to input it into the converter.

[Operation] Nonlinearity of the D/A converter is corrected in advance using the input conversion table.

[Examples] Examples of the present invention will be described below with reference to the drawings. 1st
The figure is a connection diagram showing one embodiment of this invention.
is the input digital signal Dr, 2 is the input conversion table, 3
is a conversion digital signal input DV, 4 is a D/A converter, 5
is the output analog signal Av.

FIG. 2 is a diagram showing the stored contents of the input conversion table 2 in FIG. 1. The input conversion table 2 is configured in the form of ROM (read-only memory), etc. The value of Dv corresponding to is read out. FIG. 2 shows the contents of the input conversion table 2 corresponding to the D/A converter 4 having the characteristics shown in FIG. 3 Ar, and below, a method for creating the table shown in FIG. 2 from the characteristics shown in FIG. . In order to make the input/output characteristics linear, it is sufficient to give an output of Av to an input of Dr (in reality, an output of Ar is obtained). In order to obtain an output of Av with this D/A converter 4, it is sufficient to input Dv as an input.

That is, it is sufficient to convert Dr to Dv using the input conversion table 2. In this way, Dv is determined for each part of Dr, and this is stored to create the input conversion table 2.

Therefore, Drl and Av5 in FIG. 1 have a linear relationship.

In the above description, an example using the input conversion table 2 as hardware has been described, but input conversion may be performed under program control by a processor.

[Effects of the Invention] As described above, according to the present invention, the linearity of D/A conversion can be improved with a simple device.

[Brief explanation of the drawing]

FIG. 1 is a connection diagram showing an embodiment of the present invention, FIG. 2 is a diagram showing the contents of the input conversion table of FIG. 1, and FIG. 3 is a diagram showing nonlinearity of input and output in a conventional device. 1... Input digital signal Dr, 2... Input conversion table, 3... Conversion digital signal input Dv, 4...
- D/A converter, 5... linear analog output signal. Note that the same reference numerals in the figures indicate the same or corresponding parts.

Claims (1)

[Claims] A D/A converter that outputs each value of an output analog signal Ar corresponding to each value of an input digital signal Dr, assuming that the input/output characteristics of this D/A converter are linear. Then, each value of the hypothetical analog signal output Av corresponding to each input digital signal Dr is calculated, and in the D/A converter,
A converted digital signal input Dv is calculated in which an analog signal of the value of Av is output corresponding to each value of the above Av, and each value of the input digital signal Dr is used as an address to calculate a converted digital signal input Dv corresponding to this. means for creating an input conversion table for storing each value of the input conversion table, inputting the input digital signal Dr to the input conversion table, and inputting a converted digital signal input Dv, which is an output of the input conversion table, to the D/A converter; D characterized in that it is equipped with means for converting the signal into an analog signal output.
/A conversion device.