Direct determination of the ultimate performance of the RSFQ digital devices and Single Flux Quantum Voltage Amplifiers

In spite of the SFQ elements itself can operate at frequencies much higher than 100GHz there are some effects that might considerably decrease this value in real digital circuits. Most of these effects are due to the connection of the elements with the Josephson transmission lines. To build the complicated digital circuits one need to have fault free switching elements, relevant high frequency Josephson generator with stable repetition pulse rate and the possibility to prevent the high frequency mutual phase locking between the signal and clock generators. Here we suggest simple experiments to investigate the mentioned above problems experimentally. The number of fault-free switching of the SFQ elements was determined by investigation of SFQ pulse propagation in the ring Josephson transmission line closed with SFQ invertor. The lifetime morp than few hours was obtained that corresponds to at least 1013 fault-free switching. The completely DC powered SFQ sampler was sent to directly measure a repetition rate stability of the Josephson generator loaded by uniformly shunted transmission line. The stable repetition rate up to the 7GHz was obtained. We report also the experimental results for two stages serial and five stages parallel quasi digital amplifiers. The precision calculation of the input SFQ pulses is the main idea of these circuits.