You can adjust the current by changing the 62 ohm resistor.The current is 62/0.6 (62ohm/Vbe).In this circuit the current os 11.5mA.
The load is 1kohm resistor.
You can change it between 0-1kohm and the current is constant.if you use the upper value resistor than the 1kohm the current will begin to reduce its value.
