Negative Resistance Quasiparticle SIS Amplifiers

Lumped element as well as distributed negative resistance amplifiers utilizing the negative slope of the voltage-current characteristic of the quasi-particle current in SIS tunnel junctions are investigated. The gain and the noise figures of both amplifier types and the gain-bandwidth product of the lumped element amplifier are computed. Numerical results for lead-aluminium SIS junctions are presented. Negative resistance SIS amplifiers are promising for future realization of sensitive amplifiers up into the terahertz range.