I recently got interested in signal processing and amplifiers. In the following file "Two_port_network_bjt" on the first page i could simplify a simple common emitter amplifier with two ports. Afterwards i think its easier to tell the input impedance Zi, ouput impedance Zo and the voltage gain Vu...

Am i right if:
(without R load and R collector)

Zi = (B+1)*RE+rBE
Zo = RE+rCE

Vu = VCE/VBE = (RE-BrCE) / ((RE+rCE) * ((B+1)*RE+rBE))

On the second page i am stuck at this collector feedback circuit with emitter resistor RE and feedback resistor RF. Could please anybody help me out or give an advice and correct me if i made a mistake? Its not clear how the two port would look like if there is this RF resistor.

 

Hello Hangster, the circuit at page 2 is correct.
I think you need to name the voltage at positive terminal of Re as, say, Vx, and solve it in terms of Vin, using KCL and KVL.

 

Hello debut123, firstly thank you for your response.

I am quite sure what you mean, but if i get this equations with KCL and KVL and after merging them, there is one equation left with Ic or B*IB, which i can't get rid of by using two port rules...

Maybe i do not see the trick hiding behind this circuit, nethertheless i have already contacted a teacher on my university and hopefully i will get an answer