A Transistor Only Sigma-Delta A/D Converter for a CMOS Speech CODEC

This paper describes the design and measurement results of a 1-bit A/D converter based on a transistor only switched current (SI) second order sigma-delta modulator. The 1-bit A/D converter was simulated and processed in ES2 1.5 μm CMOS technology. The second order filter is based on class AB current-integrators. Measurement results on the first silicon show this circuit technique promissing for speech CODEC A/D conversion.