High current gain HTS Josephson vortex flow transistors

We have fabricated discrete Josephson vortex flow transistors from yttrium barium copper oxide thin-films on 24 degree strontium titanate bicrystals. The devices have an asymmetric design with the control current fed through an independent control line. We have measured high current gains, in excess of 20 at 77 K for a range of several devices, and substantially higher at lower temperatures. The performance at 77 K has been studied and compared with theoretical simulations, which have included the effects of noise.