I want to understand how biasing was chosen for BFP420 bjt transistor. I cant find any I-V (Ib) curves in BFP420 datasheet. Prevously i biased FET ne3210s01 and it was pretty convient, because there was some I-V curves, where i can draw Q point and load line. Although it was for certain conditions. But here, with BJT i do not know how to do that. So i did some forward and reverse calculations:
As you see i found that
VCE is around 4v and current Ie=15ma. Then Rb and Rc was determined. Sow how, based on bfp420 datasheet i can choose emitter current and Vce? Or how i can know iv characteristics. Did i choose beta(hfe),etc. right?
I have datasheet. Problem is i do not know how to read it. Currently i think using spice model to find iv curves. But there must be some way to quickly do approximate conclusions based on datasheet values. Some rule of thumb for choosing q point and load line.
IV curves cannot be used because the hFE of any transistor part number and the base-emitter voltage are a range because some of the transistors are more sensitive and others are less sensitive. The curves on a datasheet and a simulation show only a "typical" device but the circuit you design must have enough negative feedback so that it works with a minimum or a maximum transistor. The minimum and maximum spec's are guaranteed and are printed in the datasheet.