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Low-temperature MOS devices (77 K) present significant gain in speed and density for a low technological cost. An N-MOS process has been adapted for use at liquid-nitrogen temperature using argon-implanted polysilicon resistors of very small dimensions as loads, instead of depleted devices. A ripple-carry 3-bit adder has been designed with 3- and 2.4-μm roles to estimate the speed-power possibilities of the technology. It uses complex gates with quasi-static memorizing, and yields a maximum measured frequency of 405 MHz for a 28-mW power consumption, with 2.4-μm design rules. This can be compared with results from the same circuit realized with other technologies (GaAs, 1-μm N-MOS,˙˙˙).