In the above circuit, the current is a constant independent of provided the transistor if in the active region, as in the active region, is determined by . is assumed to be 1K.
Further, we also want the maximum power to be less than a certain value, say, 1 Watt. We have,
Therefore, for the circuit to work, we must have,
We would obviously like to increase the range for which this current source works. In the same circuit, if we now take , we get with similar calculations,
This is a much better situation.