This paper reports a manufacturable AlGaAs/GaAs heterojunction bipolar (HBT) technology, and development of HBT circuits for analog to digital conversion. HBT voltage comparators operated well above 10 GSps. Sample and hold circuits worked at 2 GSps with less than ??40 dB distortion. Multi-GSps 4-bit quantizers and 6-bit ADCs were realized. Multi-GSps 8??bit ADCs as well as high-high-resolution sigma-delta ADCs, based on this HBT technology, are being developed.