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Akira AKAHORI Akito SEKIYA Takahiro YAMADA Akira FUJIMAKI Hisao HAYAKAWA
We have designed the Half Adder (HA) circuit and the Carry Save Serial Adder (CSSA) circuit based on pipeline architecture. Our HA has the structure of a two-stage pipeline and consists of 160 Josephson Junctions (JJs). Our CSSA has the structure of a four-stage pipeline with a feedback loop and consists of 360 JJs. These circuits were fabricated by the NEC standard process. There are two issues which should be considered in the design. One is parameter spreads generated by the fabrication process and the other is leakage currents between the gates. We have introduced a parameter optimization method to deal with the parameter spreads. We have also inserted three stages of JTLs to reduce leakage currents. We have experimentally confirmed the correct operations of these circuits. The obtained bias margins were 33.1% for the HA and 24.6% for the CSSA.