A chain circuit of direct coupled logic gates consisting of niobium nitride (NbN)‐lead (Pb) alloy electrodes has been fabricated. The junctions used were of 1.5 &mgr;m square and had a current density of 20 kA/cm2. A special sampling method with jitter of ±1.5 ps was used to precisely measure the short delay time. A minimum logic delay of 5.6 ps/gate has been obtained with a fan in=fan out=1 structure.