Circuits, methods, and apparatus that provide differential-input, single-slope, column-parallel analog-to-digital converter (ADC) architectures for use in high-resolution CMOS image sensors (CIS) are described. A column ADC is coupled with a column of a pixel array and configured to convert a pixel signal level to a corresponding digital output value according to a ramp generator output. Each pixel is configured to output a pixel reset level and a pixel signal level at different operating stages, and the ramp generator output includes a ramp reset level and a ramp signal level at the same or different at different operating stages. The pixel and ramp outputs are used to differentially drive a comparator stage of the column ADC, for example, to reduce power supply noise.