Consider this picture, a) and b). [PLAIN]http://pokit.org/get/f0af323a103c1d29539836143a7784a1.jpg [Broken] Now I am getting confused a bit here. a) I know that the first picture represents a bias for current source. And we change the value on the potentiometer the current will stay the same. (considering we won't go too far and put transistor into saturation) From the computations I got, and simulations in national instruments, I can say that the base current is adjusting accordingly in order to keep the current constant. I can handle that idea, I think. b) Will the same happen here? If I change the potentiometer. Consider that resistor connected to base to be thevenin equivalent of those 2 voltage dividers and that voltage source at base to be also be within thevins theorem. And every other parameter stays the same. But I have the feeling that the base current here is determined only by that voltage source at base and that resistor, hence it won't change when I change the potentiometer, hence the current in collector must fall. Are those to schemes one and the same? Will I have the same effect?