18 May 1988 Flash-Type A/D Converters And Shift Registers
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We have studied a variety of circuits for low-accuracy (4-bit) A/D converters; these have been of two types. The "periodic-threshold" type requires only one comparator for each bit. The "fully parallel" configuration requires one comparator for each digital level (15 for 4 bits). Results for both types of A/D converter will be sum-marized. The periodic-threshold type of circuit depends on the quan-tum interferometric property of Superconducting QUantum Interference Devices (SQUIDs). Periodic-threshold circuits using two junction SQUIDs are limited to 1-2 GHz of analog bandwidth. Two different circuits for the fully parallel type of A/D converter circuit have been studied. One employs latching comparators for each of the levels and the comparators drive a novel binary encoder. Simulations show that the analog bandwidth is at least 3.5 GHz. Another fully parallel A/D converter circuit uses the bistability of a single junction SQUID to achieve high sensitivity, and the rapid switching of such a SQUID to obtain the short aperture time needed for wideband A/D conversion. Simulations indicate an analog bandwidth of about 5 GHz. Our simulations of shift-register circuits show that a circuit with a three-phase clock and three AND gates per bit can operate at least to 25 GHz. A two-phase circuit, in which current is diverted to one or the other branch of a superconducting loop to indicate a "1" or "0," has been shown by simulation to operate correctly when clocked at 62.5 GHz.
© (1988) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
D. A. Petersen, D. A. Petersen, V. Nandakumar, V. Nandakumar, E. Fang, E. Fang, D. F. Hebert, D. F. Hebert, T. Van Duzer, T. Van Duzer, } "Flash-Type A/D Converters And Shift Registers", Proc. SPIE 0879, Sensing, Discrimination, and Signal Processing and Superconducting Materials and Intrumentation, (18 May 1988); doi: 10.1117/12.943981; https://doi.org/10.1117/12.943981


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