Elimination of output voltage quantization in the vortex flow transistor

The authors discuss, in theory, the problems associated with quantization in the output voltage of the vortex-flow transistor (VFT) and investigate practical solutions. Removing the quantization from the junction flux flow steps is shown to be a nontrivial problem. Termination of one boundary of the junction seems to be the most elegant solution. Numerical solutions to the sine-Gordon equation show that a linear RC termination can remove the staircase structure from a junction's flux flow branch by eliminating boundary reflections of fluxon energy. This simple solution is hard to effect because thin-film components of the proper dimensions and values are difficult to realize in the laboratory. The addition of shunting loss to the junction is an alternate solution. It involves adding a distributed loss across the length of the junction to reduce the Q of the cavity resonator produced by the junction electrodes. A decrease in Q increases the voltage width of the individual resonances which make up the flux flow branch at low voltages. If the voltage width of each resonant mode is as large as the voltage separation of each mode, the quantization is removed.< >