Gain limitations in narrow width Josephson junction vortex flow transistors

The number of devices required to achieve a practical gain from a Josephson junction vortex flow transistor (JVFT) distributed amplifier is inversely proportional to the gain or the transresistance, r/sub m/ of each active device. A large number of devices means longer transmission line lengths associated with increased loss and size. Reducing the junction width results in increased r/sub m/, however there is a fundamental limit for achievable r/sub m/. This is basically due to two reasons, increased fringing field effects and edge penetration at smaller aspect ratios. Field analyses made on devices with various dimensions show this limitation in the magnitude of r/sub m/ for narrower junctions. The analysis also provides valuable information on parasitic elements in the circuit model for a JVFT. Results of the analyses on devices having different geometries suitable for high frequency operation are presented.<>