A/D converter and solid-state imaging apparatus with offset voltage correction

Abstract

Provided is an A / D converter including an input terminal, a reference signal line for supplying a reference signal which changes temporally, a comparator, a correction capacitor connected to an inverting input terminal of the comparator; and an output circuit which outputs digital data corresponding to an analog signal input to the input terminal. In a first state in which a total voltage of a first analog signal and an offset voltage of the comparator is held in the correction capacitor, a second analog signal input to the input terminal is supplied to a non-inverting input terminal of the comparator, and the second analog signal or the total voltage is changed using the reference signal, thereby outputting, from the output circuit, digital data.

Description

BACKGROUND OF THE INVENTION[0001]1. Field of the Invention[0002]The present invention relates to an A / D converter and solid-state imaging apparatus.[0003]2. Description of the Related Art[0004]A technique which arranges A / D converters in correspondence with columns of pixels arranged in an array and converts signals from the respective pixels into digital data in a solid-state imaging apparatus is known. However, since offset voltages of comparators included in the respective A / D converters are different, an A / D conversion period has to be set in consideration of a maximum value of the offset voltages. U.S. Pat. No. 7,671,908 has proposed a technique for correcting an offset voltage by feeding back an output of the comparator included in each individual A / D converter to an input of that comparator.SUMMARY OF THE INVENTION[0005]The technique of U.S. Pat. No. 7,671,908 uses a controller to feed back the output of the comparator to its input. For this reason, the circuit arrangement of...

AI Technical Summary

Benefits of technology

[0005]The technique of U.S. Pat. No. 7,671,908 uses a controller to feed back the output of the comparator to its input. For this reason, the circuit arrangement of the A / D converter is complicated, and noise caused by the controller adversely influences the output of each comparator. Hence, an aspect of the present invention provides a technique for correcting an offset voltage of a comparator of each A / D converter by a simple arrangement.

Problems solved by technology

For this reason, the circuit arrangement of the A / D converter is complicated, and noise caused by the controller adversely influences the output of each comparator.