Vbe 2 . The circuit in figure 1 was simulated. Vbe 2 was varied and the collector currents were observed.
Collector currents depend on base emitter voltage.
At low currents the Vbes of the two transistors are nearly equal, because the drop across R is small, and I 1 is greater than I 2 because N1 is bigger. As the base voltage increases, currents increase. The current in N 1 is limited by R to increase linearly, while the current in N 2 increases exponentially with Vbe 2 .