CMOS implementation of an immediately adaptive delta modulator

Abstract

The modulator is described at the system level by analyzing the system transfer function, stability, frequency response, and quantization noise. Individual circuit blocks are explained at device level. A comparator design which is based on presenting an amplified signal to a pull-up pull-down latch, commonly used in dynamic RAMs, is described. The immediately adaptive delta modulator (IADM) was fabricated in a 3.5-/spl mu/m twin-tub CMOS process. An experimentally measured signal-to-noise ratio of 91 dB across the audio band (20 Hz-20 kHz) with a total harmonic distortion of less than 0.17% is reported. These results demonstrate the potential of this topology for 16-bit audio-band A/D conversion.