High Voltage Driver for RSFQ Digital Signal Processor

We present an Rapid Single Flux Quantum (RSFQ) based high voltage driver (HVD) developed for the first amplification stage of a hybrid semiconductor-superconductor memory interface for the RSFQ digital signal processor. Implementation of the driver allows to eliminate the impedance mismatch between RSFQ and standard 50 Omega input of semiconductor electronics and increases the signal-to-noise ratio to reach reliable signal transmission with sufficiently low bit error rate. The driver design is based on the serial stack of 8 SQUIDs with specially configured ground-cuts that form a quasi-coplanar line with 50 Omega impedance. The impedance of the driver has been extracted using 3D EM simulators that accurately take into account multilayer structure and capacitance to the ground. The circuit has been designed for the Hypres 4.5 kA/cm
²
process. The driver was simulated numerically in PSCAN. The driver can produce output signal at 1 Gbit/s speed and 2.4 mV signal level that is enough to be sensed by low-noise amplifier on the further amplification stage.