Design and demonstration of SFQ pipelined multiplier

We have designed an SFQ pipeline multiplier using a cell-based design method. The cell-based design method enables us to expand the circuit-scale easily and is essential for the design of large-scale circuits. In the construction of the multiplier, a serial-parallel type was adopted. This type performs the partial products and the summation of the products in a bit-serial form. The multiplier designed here is a 3-bit serial-parallel structure with a seven-stage pipeline and is composed of destructive read-out (DRO) gates, nondestructive read-out (NDRO) gates and carry save serial adders (CSSA's). This circuit was fabricated by the NEC standard process. The number of Josephson Junctions is 1150. We have successfully tested the full operation with a bias margin of ±5.5%.