A niobium nitride-based analog to digital converter using rapid single flux quantum logic operating at 9.5 K

An analog to digital converter (ADC) using the rapid single flux quantum (RSFQ) logic family implemented in niobium nitride (NbN) technology is described. The circuit was originally developed and demonstrated in niobium technology. An identical circuit was then laid out, fabricated and demonstrated in NbN technology. The chips were fabricated using an eight-layer NbN-based process with Josephson junction critical current density of 500 A/cm/sup 2/. In this paper, we report on the measurement results for a 6-bit flux quantizing ADC which exhibited proper operation and good DC bias margins. We also demonstrate results from an ADC chip operating up to 9.5 K.>