A time-of-flight distance measurement sensor is presented. Detection and mixing is done with an in-substrate current assisted photonic demodulator. Background light suppression and high dynamic range is achieved using a variable transimpedance amplifier. The pixel also comprises sample and hold circuitry and special low pass filters, for in-pixel averaging, with a 10 Hz to 10 kHz tuneable cut-off frequency. Proof-of-principle measurements on a standard CMOS 0.35 um prototype measuring 50 um x 50 um with a fill factor of 60\% are included.