CMOS self-calibration of Josephson flash-type A/D circuits

We present CMOS self-calibration and bias circuits for Josephson circuits. In Josephson technology, process variations in critical circuit parameters such as junction critical current, resistance, and inductance adversely affect the performance. For example, process deviations in junction critical currents leads to low dynamic range and nonuniform quantization steps in flash-type A/D converters. While CMOS technology has a speed disadvantage with respect to Josephson technology, it does make available highly accurate current sources that are relatively process independent and difficult to obtain in Josephson technology. Here, we discuss how the 4 K CMOS self-calibration of a Josephson flash type A/D converter can be used to improve dynamic range.<>