Measurements of dynamic range and linearity of flux-quantizing A/D converters

High-precision measurements of the linearity of a flux-quantizing analog-to-digital converter (ADC) using a pair of 6-b rapid single-flux-quantum (RSFQ) counters have been made. The sensitivity and dynamic range of the ADC were 13.3 mu A/least significant bit (LSB) and +or-30 mA, respectively (12 b). The conversion curve was measured with an accuracy of +or-7.5% of LSB within a dynamic range of 9 b and exhibited no evidence of nonlinearity. In addition, tests have been made on stand-alone flux quantizers with dynamic range up to 16 b, and a unidirectional 12-b ADC which directly demonstrated a correct divide-by-2/sup 12/ operation with a 10-GHz, 4 LSBs sinewave input signal (peak counting frequency in excess of 80 GHz).<
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