A time-of-flight image sensor including a readout circuit is provided. The readout circuit may include a pixel array including multiple pixels. The pixel array may be configured to produce a pixel signal for each of one or more pixels over a series of timesteps. The pixel signal may include an illuminated value and a reset value. The readout circuit may further include a plurality of gain selection comparators configured to receive the pixel signal and select an amplifier gain value. The readout circuit may further include analog correlated double sampling circuitry. The readout circuit may further include a programmable gain amplifier configured to generate an amplified pixel signal from the pixel signal, which may be amplified at the selected amplifier gain value. The readout circuit may further include a plurality of analog-to-digital converters. Each of the analog-to-digital converters may have a common ramp generated by a global ramp generator.