Ramp generator and pixel column readout circuit

Abstract

The invention provides a ramp generator. The ramp generator comprises a first switch; an operational amplifier, wherein the first input end of the operational amplifier is connected with analog voltage through a first switch, the second input end of the operational amplifier is connected with reference voltage, the output end of the operational amplifier outputs ramp signals, the output end is connected to the first input end through a reset capacitor, and an offset voltage is generated at the first input end; a second switch which is connected with the reset capacitor in parallel; a third switch which is connected in series between a reset capacitor and the second switch; and a fourth switch which is connected in series between the reset capacitor and the reference voltage, wherein when the second switch and the fourth switch are both switched on and the first switch and the third switch are both switched off, the reset capacitor stores and eliminates the offset voltage. According to the pixel column reading circuit, the offset voltage in the ramp generator can be eliminated, so that the offset voltage of the pixel column reading circuit is eliminated, and the image quality of the CMOS image sensor is improved.

Description

technical field [0001] The invention relates to electronic circuit technology, in particular to a ramp generator and a pixel row readout circuit. Background technique [0002] With the continuous development of CMOS technology, the application range of CMOS image sensors is becoming more and more extensive because of its low power consumption, simple power supply, high integration, and low cost. CMOS image sensors are used to generate images representing objects. A CMOS image sensor includes rows and columns of pixels, and pixel row readout circuits and pixel column readout circuits. A pixel produces a small photoelectric signal proportional to the light reflected from the object to be imaged. The photoelectric signal is read and processed by signal processing circuitry to produce an image representative of the object. Pixels belonging to the same column are usually connected to a common output node from which signals are read out. Each pixel in the same bit line is cont...

AI Technical Summary

Problems solved by technology

The offset voltage seriously affects the image quality of the CMOS image sensor, resulting in the reduction of the conversion accuracy of the image sensor, and the difference between the chips between different processes is large

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