High-frequency clock operation of Josephson 256-word x 16-bit RAMs

A Josephson 256-word x 16-bit RAM that includes a power circuit has been de veloped to enable high-frequency clock operation. This RAM consists of a 4 x 4 matrix array of 256RAM blocks, impedance-matched lines, and signal ampl ifiers. A power-supply circuit, composed of a transformer and a Josephson r egulator, is included in each 256RAM block Fail bit maps for the 256RAM blo ck were measured, and perfect operation with a 100% bit yield was obtained. The 256RAM block functioned up to a clock frequency of 1.07 GHz. We succee ded in feeding a large high-frequency current of more than 2 A into the ent ire 256-word x 16-bit RAM. The 256-word x 16-bit RAM therefore functioned u p to a clock frequency of 620 MHz.