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