We have been developing an analog amplifier utilizing a flux flow phenomenon in a Josephson line. i.e., Flux-Flow-Type Josephson Amplifier (FFA). The FFA converts a signal current Isto a voltage VDCacross the Josephson line, and the Is-Vdccharacteristic determines performances of FFA. such as a gain and a saturation level. Studies have been made to improve the Is-Vdcrelation, such as a transresistance r.=dVdc/dI and a linear operation range. It is shown that the transresistance can be improved significantly by reducing a width W of the Josephson line, and by utilizing a kinetic inductance of the line. The kinetic inductance can be increased by thinning the thickness t of an electrode of the line, and by using the electrode with large London penetration depth such as NbN. The obtained transresistance is as large as r.=6.8Ω for NbN/Pb-alloy Josephson lines with t=5nm and W=4μm. It is also shown that the linear operation range of the amplifier is as large as lmV. On the basis of experimental results, evaluation is made of the performances of FFA.
All Science Journal Classification (ASJC) codes
- Electronic, Optical and Magnetic Materials
- Electrical and Electronic Engineering