Hello, I have the following circuit, http://imageshack.us/photo/my-images/30/help2c.png/

I want to write Uut(t) as an expression of U(t),

Uut(t) =(h21 + 1)*IB2* ((r6*RL)/R6 + RL)

Ugs = U(t)

Now I want to express IB2 as a function of Ugs. As seen gm*Ugs is current out from the node, but Im not sure how much current will go through, RD,R4 and R5 to get IB2.

 

Here's one possible approach ....