A switched-current /spl Sigma//spl Delta/ converter for direct photodiode interfacing

A switched-current (SI) sigma-delta modulator for the direct digitisation of photodiode currents is described. The noise-shaping filter is implemented by an SI second generation grounded gate integrator, and a current driven regenerative comparator forms the single bit quantiser. Measured results are presented for an IC implemented in a 0.8 /spl mu/m standard 5 V digital CMOS process.<<ETX>>