I am currently taking a class on analog electronics and this is one of the problems that came up:
V 1 = 15V V 1 = 15V, Ueb = Ube = 0.6V, Uce(sat) = 0.2V, β =200,
VT = 25mV, R2 = 39Ω, R4 = 4.7kΩ, R5 = 470Ω
I am asked to find the values of R1, R3 and R6 such that the quiescent collector currents of Q2 and Q3 are both 8 mA, and the collector of Q2 is at the potential V1/2 when there is no input signal present(what does this tell me? Is it even relevant since I am only doing dc analysis here?) Are there any general steps to follow? I did some similar analysis with two transistors, and what always needed to be done is find expressions for Ve,Vc and Vb for each transistor and by comparing them make an assumption in which mode it is operating. Here however, I came to a contradiction, namely Q2 seems to be in linear mode, and therefore R6=(V1/2-V1-0.7)/8mA <0. I hope I didn't ask a question too broad. I am not asking for a solution, but merely to tell me the recipe for this kind of analysis.
EDIT:Awkwardly enough, I only now noticed that in fact what seemed to me as a node between the collector of Q1 and the base of q3 isn't one. One can tell just by observing carefully.