Diversified Technologies, Inc. (DTI) has developed and built a solid-state switch as a form-fit-function interface upgrade kit to replace legacy thyratron equipment. Under a US DOE SBIR for the SLAC National Accelerator Laboratory, this switch was designed using arrays of series-and parallel-connected commercial insulated-gate bipolar transistors (IGBTs). The solid-state switch's extremely long life and reliability presents an attractive replacement opportunity for many thyratron-based systems.