A fourth-order bandpass /spl Sigma//spl Delta/ modulator using current-mode analog/digital circuits

We present a fourth-order bandpass /spl Sigma//spl Delta/ switched-current modulator IC in 0.8 /spl mu/m CMOS single-poly technology. Its architecture is obtained by applying a lowpass to bandpass transformation (z/sup -1//spl rarr/-z/sup -2/) to a second-order lowpass modulator. It has been realized using fully-differential circuitry with common-mode feedback. Measurements show 8 bit dynamic range up to 5 MHz clock frequency and 10 KHz bandwidth.