This preset is the same as preset 1 except that the gap is taken independent of temperature.
In preset 1 a temperature dependence of the gap (roughly appropriate to germanium) is included to suggest some of the ambiguity associated with the interpretation of Arrhenius plots. Preset 2 assumes a temperature independent gap. To see the effect of the temperature dependent gap on the carrier concentrations, switch back and forth between presets 1 and 2. You see the gap change in the chemical potential plot but the slope of the density plot does not change. What's going on?