A TRANSISTOR-ONLY SWITCHED-CURRENT SIGMA-DELTA A D CONVERTER FOR A CMOS SPEECH CODEC/

This paper describes the design and measurement results of a 1-b A/D c onverter based on a transistor-only switched current (SI) second-order sigma-delta modulator, The 1-b A/D converter was simulated and proces sed in ES2 1.5 mu m CMOS technology, The second-order filter is based on class AB switched current-integrators. The analog current memory ce lls in the integrator are optimized for linear operation with a strong class AB overlap region to avoid class B operation and cross-over dis tortion, Measurement results on the first silicon performing 11-b reso lution show that this circuit technique is promising for speech CODEC A/D conversion.