Hey guys I don't have a scanner so bear with me a second. I was given a circuit including a NPN transistor. The collected is connected to a resistor Rc and a Vcc = 5 volts above it. The base is connected to an AC signal Vs and DC source VBB in series with one another. There is a resistor Rb = 25k between the base and those sources. Finally the emitter is connected to ground. Given B = 120 and r(pi) = 5.4k Find Vbb and Rc such that Q-Point is center of load line. Vo is also equal to Vc
So here's what I did.
DC Analysis:
r(pi) = B/gm => gm = B/r(pi) = 22.22 mA/V
gm = Ic/Vt => Vt*gm = Ic = .578 ma
Ic = BIb = 4.82uA
-Vbb + RbIb +. 7 = 0 Vbb = .8205V
So where I get stuck is trying to solve for the load line Vc=Vo versus Ic
I know ic = gmVeb where Veb = (r(pi)/r(pi)*rb) * Vs
I also knew Vc = Vo = RcIc
So I tried solving using those and got a load line equation of Vo = constant*Vs. Not what I was looking for. Your help is appreciated!
So here's what I did.
DC Analysis:
r(pi) = B/gm => gm = B/r(pi) = 22.22 mA/V
gm = Ic/Vt => Vt*gm = Ic = .578 ma
Ic = BIb = 4.82uA
-Vbb + RbIb +. 7 = 0 Vbb = .8205V
So where I get stuck is trying to solve for the load line Vc=Vo versus Ic
I know ic = gmVeb where Veb = (r(pi)/r(pi)*rb) * Vs
I also knew Vc = Vo = RcIc
So I tried solving using those and got a load line equation of Vo = constant*Vs. Not what I was looking for. Your help is appreciated!