Josephson junction to FET high speed line driver made of TlCaBaCuO.

摘要

We have used a Tl-Ca-Ba-Cu-O superconducting flux flow transistor (SFFT) as an active impedance converter between Josephson and FET circuitry. The input of the flux flow device is a control line of low impedance that can be driven by a tunnel junction. The output is the signal across the SFFT which is made of a parallel array of weak links. The output impedance is typically greater than 5 (Omega) with a maximum voltage swing of over 100 mV into a 50 (Omega) system. The switching of an all-Nb junction induced a 90 mV voltage swing at the FET input and over 200 mV at the FET output. The line driver can operate anywhere between 4.2K and 85K with minor changes in speed ((plus minus)5 ps) and output level ((plus minus)10 mV). The switching time measured was about 100 ps and was fixture limited. 13 refs., 5 figs.