Behaviors of a transistor during a dose rate event can be modeled using a
circuit simulation software package. A subcircuit model replaces a
transistor in a circuit design to be simulated. The subcircuit model can
be in the form of a schematic-based representation or a netlist. The
subcircuit model provides a model of a source junction and a drain
junction in the transistor during the dose rate event. The subcircuit
model also includes the size of the transistor being replaced and the
dose rate of the dose rate event. Once the transistor is replaced with
the subcircuit model, a dose rate simulation may be performed to
determine the dose rate hardness of the circuit design.