Input and Output Resistance (Electronics)

[Midas_Touch]

R_out
|-------------***------------o------------------|
|........+......|
|.......V_signal......* R_in
-..V_out, perfect..........*
-.............|
|.............|
|........-.....|
|-----------------------------o------------------|
=...(ground).........=

Say that circuit 1 is the left side of the above circuit (ignore the dots), and circuit 2 is the right side (R_in).

First I have to find V_signal using kirchhoff rules
so I get V_signal -R_out - V_out, perfect - R_n = 0

But I am not sure what happens with R_in >> R_out, R_in << R_out or when R_in = R_out.

 

[quantumdude]

I can't make heads or tails of your equation.

V_signal -R_out - V_out, perfect - R_n = 0

Do you mean this?

V_{signal}-R_{out}-V_{out,perfect}-R_n=0

That's what it looks like, but if that is in fact the equation that it makes no sense. You're subtracting voltages and resistances, which have totally different units.