JPS63294130A - Digital/analog converter - Google Patents

Abstract

PURPOSE:To reduce the distortion produced at the time of small signals, by constituting a digital/analog (D/A) converter of a constant multipier and constant adder, which make digital operations, D/A converter, and band-pass filter. CONSTITUTION:This D/A converter is constituted of a constant multiplier 2 and constant adder 3, which make digital operations, D/A converter 4, and band-pass filter 5. The constant multiplier 2 multiplies digital signals inputted from an input terminal 1 by a constant and the constant adder 3 adds a DC offset to the digital signals. Then the D/A converter 4 performs D/A conversion on the output of the adder 3, but, since the digital signals have the offset and the signals after the offset do not cross the bipolar-zero point of the D/A converter 4, large distortion is not produced. Therefore, the distortion produced at the time of small signals can be made smaller.

Description

[Detailed Description of the Invention] [Field of Industrial Application] This invention relates to digital/analog conversion (hereinafter referred to as D'
/ A conversion) device.

[Conventional technology]

D/A used in digital audio playback equipment
There are many types of converters, but the most common ones are
As shown in FIG. 2, the current value is i.

1/2i, ]/4i 1/2"-"i, n current sources 10ILp 10h, -I Qn, corresponding switches lla, llb...11n, and switch drivers 12a, 12b... 12n It is made up of.

[Problem that the invention seeks to solve]

In the conventional D/A converter with the configuration shown in Figure 2, it is difficult to reduce the error at bipolar zero, where all pits are reversed, due to the accuracy of each current source, the characteristic difference between each switch, etc., and it is especially difficult to make adjustments. If not provided, the largest error will occur here.

Most digital audio playback devices use these four bipolar points as signal zero points, so
As shown in FIG. 3, zero-crossing distortion occurs, and the distortion becomes particularly large when the signal is small.

This invention was made to solve the above-mentioned problems, and aims to provide an I/A converter that does not require high accuracy (i.e., can reduce distortion at the time of small signals). .

[Means for solving problems]

The D/A converter according to the present invention is composed of a constant multiplier and a constant adder using digital operations, a digital/analog converter, and a bandpass filter.

[Effect]

The bipolar zero point of the D/A converter in this invention is
Due to the offset by the constant adder, it does not coincide with the zero point of the signal, and signals below this offset are not affected by the distortion that occurs at the bipolar zero point.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings.

In Figure 1, a constant K is applied to the input digital signal.
3 is a constant adder that adds a constant to the output of constant multiplier 2, 4 is a D/A converter, and 5 is a bandpass filter (hereinafter referred to as 6 is an output terminal for outputting a reproduced analog signal.

Next, the operation will be explained. Multiply the digital signal input from input terminal 1 by a constant K in constant multiplier 2, and add a DC offset (constant L) to the digital signal in constant adder 3. At this time, if the peak value of the D/A converter 4 is exceeded,
Since the polarity of the signal after D/A conversion is reversed, constants are selected to satisfy the following equation.

(Peak value of D/A converter 4) As shown in the figure, since the signal below the offset does not cross the bipolar zero point of the D/A converter, it does not cause large distortion as shown in FIG.

When unnecessary band components are removed from the output of the D/A converter 4 by the BPF 5, an analog signal from which the DC offset added by the constant addition N2 has been removed is output to the output terminal 6.

Also, at the signal level that crosses the bipolar zero point,
The change in distortion caused by adding an offset is small.

〔Effect of the invention〕

As described above, according to the invention of B, when the signal is small, it does not cross the bipolar zero point of the D/A converter, so an analog signal with low distortion can be obtained without using a high precision D/A converter. It has the effect of

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a D/A converter according to an embodiment of the present invention, FIG. 2 is a diagram showing a D/A conversion output waveform according to the present invention, and FIG. 3 is a diagram showing a conventional D/A converter. The circuit configuration diagram, FIG. 4, is a diagram showing the output waveform. In the figure, 2 is a constant multiplier, 3 is a constant adder, and 4 is D
/A converter, 5 is a band pass filter. Agent Masuo Oiwa (2 others) 1 square Figure 4: "/A reward number 5: Pan Y" 0 Matata Furuta Fang 2 Figures

Claims (1)

[Claims] A constant multiplier and a constant adder using digital operations;
A digital/analog conversion device comprising a digital/analog converter and a bandpass filter.