An experimental digital SQUID with large dynamic range and low noise

A digital SQUID chip designed for large dynamic range and intrinsic sensitivity as good as an analog SQUID was fabricated and tested. It consists of a pickup coil, a SQUID amplifier, edge-triggered latching comparators, and a feedback loop using an integrating single-flux-quantum D/A converter. Proper operation of the chip was demonstrated, with the output one-bit data stream averaged and integrated to reconstruct the input signal. A sampling rate up to 500 MHz was achieved.<
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