| 摘要 |
PURPOSE:To detect a superconductive current by using a comparator for amplifying in lock-in mode the output of a DC magnetic flux parametron (DCFP) circuit as an exciting current and a reference input, extracting the exciting current and its frequency component, feeding back and reducing the component to zero. CONSTITUTION:The DCFP circuit is excited by a positive unipolar pulse current of frequency fo. If an input current IS dependent upon the magnetic flux to be detected is larger than a reference current Ir, a positive pulse string synchronized with a current 110 appears as an output current IL, a negative pulse string appears in case of IS<Ir, and when IS=Ir is formed, positive and negative polarity pulse strings appear at the same probability, so that the coincidence between the IS and Ir can be decided. The output IL is lock-in amplified 201 by referring fref(=fo) synchronized with the exciting current 110 and a component fo is extracted. The amplified output 201 is positive in case of Ir<IS, negative in case of Ir>IS and zero in case of IS=Ir. When the output is inverted against the input and used as a reference current for the DCFP circuit, a feedback system converging so as to form IS=Ir is constituted. In said constitution, a current comparator having high performance can be obtained and a superconductive current can be detected hollowing a highly sensitive and rapid signal.
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