Components for a GaAs delta-sigma modulator oversampled analog-to-digital converter

The authors examine the design issues, alternatives, and problems of a GaAs delta-sigma modulator. Components for a delta-sigma modulator are designed and fabricated in a depletion-mode GaAs MESFET technology. They are individually characterized and are integrated together into a second-order delta-sigma modulator. Valuable design principles are recommended for future GaAs delta-sigma modulators. Although it did not meet its initial goals, the first attempt demonstrates the modulator's noise shaping ability, which enables it to perform beyond the precision of the individual GaAs components. The modulator achieved 9-10-b performance for a 200-MHz sampling rate and 2-MHz output word rate. Components such as the comparator and 1-b DAC (digital-to-analog converter) limited the performance of the modulator. Nevertheless, corrections and improvements were identified for future GaAs delta-sigma modulator components.<>