I'm analyzing a ciruit which contains TIP31 NPN transistor. The hFE (current gain) on the datasheet is 25 (Vce = 4V, Ic = 1A), 10 to 50 (Vce = 4V, Ic = 3A). The circuit is about a battery charger and it handles various voltage, i.e. The hFE on the datasheet changes in different voltages or it maintains same range?
I looked at the graphe about hFE but it only shows of 4V test with Ic variation.
My question is how do I estimate the hFE of a transistor which is used different setting compared to the datasheet?