The authors present 4- and 12-b shift registers capable of operating from DC up to 8.56 and 4.24 GHz, respectively. These circuits' total on-chip power dissipation is estimated to be roughly 10 nW. A novel clock current distribution network permits such high clock frequency and such low on-chip power dissipation. The clock is applied as a standing wave and is distributed by inductive division. With this clock current distribution scheme, no power is dissipated along the clock lines. In spite of the circuits' low output amplitude (tens of microvolts) and of the large crosstalk with the clock frequency, the output waveforms are captured in time domain at microwave frequencies. Also, for the 12-b device, 10/sup 15/ error free operations per quantum flux parametron (QFP) are demonstrated. Finally, the 12-b shift register is the largest QFP circuit reported to date; it is composed of 48 QFPs and one DC SQUID.
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