Behaviour of HTS Josephson vortex flow transistors

We have studied both theoretically and experimentally the low-frequency beh aviour of discrete HTS Josephson vortex flow transistors. The devices were fabricated from YBa2Cu3O7 thin films grown on 24 degrees SrTiO3 bicrystal s ubstrates. They consist of an asymmetric array of 10 or 20 Josephson juncti ons, with a control current fed through an independent line that is inducti vely coupled to the array. We have measured current gains up to 40 at 77 K and substantially higher at lower temperatures. We discuss the results of s imulations of the device behaviour and consider the effects of junction cri tical current, number of junctions and array loop inductance. We compare th e measured device behaviour at 77 K with simulations which include the effe cts of thermal noise. (C) 1999 Elsevier Science B.V. All rights reserved.