We demonstrate low-voltage operation of a CMOS imager with an in-pixel large-gain comparator without degradation of the dynamic range by using a pulse-width-modulation scheme in pixel readout. Experimental results showed a dynamic range of 57 dB with a 1.0 V power supply voltage at the pixel array block, which demonstrates the possibility of low-voltage, single-power-supply operation of imagers fabricated with deep-submicron CMOS technologies.