A track-and-hold circuit based on the nonlinear quasiparticle conductance of superconductor-insulator-superconductor junctions

A new high-speed track-and-hold circuit is proposed and demonstrated. The current in a large inductor follows the instantaneous signal in the track mode and is nearly stationary in the hold mode. Control of track or hold mode is by means of lateral, balanced injection through a bridge of superconductor-insulator-superconductor (SIS) junctions. The high resistance subgap state is used for tracking and the low differential resistance at the energy gap is used for holding. Experimental results using a 6 GHz clock and signal frequencies up to 3.2 GHz are reported.< >