A/D converter

Abstract

In an A / D converter, each preamplifier (102) is provided with a preamplifier gain adjusting circuit (109). The preamplifier gain adjusting circuit (109) suppresses gain of the preamplifier (102) only when a potential difference between positive and negative outputs from the preamplifier (102) exceeds a reference potential, and limits the potential difference between positive and negative outputs from the preamplifier. Therefore, in a status where the frequency of an input signal to the A / D converter is high, even when the gain of the preamplifier is high due to variance in a manufacturing process, temperature change, power supply voltage change and the like, output strain of the preamplifier is not easily generated and characteristic deterioration of the A / D converter is suppressed.

Description

technical field [0001] The invention relates to an A / D converter with a preamplifier column and a comparator column. Background technique [0002] Conventionally, in an A / D converter that achieves high speed, area saving, and power saving, as shown in FIG. 1002 of preamplifier columns 1003 . The comparator column 1005 is generally configured to interpolate the output voltage of the preamplifier column 1003 and perform a comparison operation at the same time. The effect of disposing the preamplifier row 1003 at the front stage of the comparator row 1005 and the effect of interpolating the output voltage of the preamplifier row 1003 and performing the comparison operation at the same time can be listed as follows: first, A / D conversion can be reduced The input capacitance of the device, the second can alleviate the offset (offset) that each comparator has, and the third can make the input dynamic range of each comparator 1004 larger, etc. (For these effects, for example, ref...

AI Technical Summary

Problems solved by technology

[0005] However, in order to reduce the offset of each comparator of the A / D converter, it is necessary to increase the gain of the preamplifier

[0006] However, in conventional A / D converters, if the gain of the preamplifier becomes too high due to variations in the manufacturing process, temperature fluctuations, power supply voltage fluctuations, etc., the potential difference between the positive output and the negative output of the preamp will also change. That is, the fluctuation of the positive and negative output potential difference is too large, the frequency of the input signal of the A / D converter increases, and then the output of the preamplifier is prone to distortion. If interpolation is performed near the intersection point of the negative output, large errors will also occur due to the distortion of the preamplifier, resulting in deterioration of the characteristics of the A / D converter.

Also, if the gain of the preamplifier is too high and the output range of the preamplifier exceeds the input range of the comparator, the responsiveness of the comparator will deteriorate, so there is a problem that the characteristics of the A / D converter will deteriorate.

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