Current source for grounded loads.It is a 0-400 ohm current source.For the loads above 400 ohm the transistor is in the saturation region.Between 0-400 ohm, the transistor is in the active region.
The load is the collector resistor.There are no Vbe offset or tehir variations with temperature, Ic , Vce , etc. to worry about .It is a current source because the current is fixed if the load is changed between 0-400 ohm.So The current is independent of the load.
