1 GHz GaAs ADC building blocks

Discussed the development of commercial GaAs ICs for high speed, 6-bit, 1 Gsample/s data acquisition, using a low-cost conventional D-MESFET technology. First-generation S/Hs (sample-and-holds) and comparators are considered. Diode-bridge and FET-switch S/Hs are compared; best performances have been achieved with diode-bridge switches: 1 ns, 6-bit. Comparators provide 6-bit sensitivity at 1 GHz, but require offset adjust. Second-generation ADC (analog-to-digital converters) building blocks are also discussed. The auto biased differential input stage has been developed which is suitable for 4-bit ADC. A dynamic cell involving autocalibration techniques is required for 6-bit ADC. Using these blocks, a 4-bit 1-Gs/s full Nyquist single-ship ADC, including an S/H, has been designed. A 6-bit ADC is under design.<
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