Cmos image photographing device for correcting gain by itself and ramp signal generator comprised in the same

A CMOS image photographing device for self-correcting gain characteristics and a ramp signal generator thereof are provided to check gain characteristics of a testing analogue digital converter anytime regardless of operation of a normal analogue digital converter, thereby testing gain characteristics of the normal analogue digital converter. A CMOS image photographing device for self-correcting gain characteristics includes a pixel array(311), preferably, an APS(Active Pixel Array), an RAMP signal generator(321), a normal A/D converter(331), a test A/D converter(341), and a digital signal controller(351). The RAMP signal generator generates a ramp signal(Vramp) in response to a ramp control signal(Vcon) output from the digital signal controller. The normal A/D converter is preferably a columnar A/D converter and converts an analogue signal(AN1) output from the pixel array to a digital signal(D1) in response to the ramp signal. The test A/D converter converts a test analogue signal(AN2) output from the digital signal controller to a digital signal(D2) in response to the ramp signal. The test A/D converter is formed in the same conditions via the same procedure with the normal A/D converter, thereby exhibiting the same operation characteristics with the normal A/D converter.