# Input and Output Resistance (Electronics)

1. Oct 6, 2005

### 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 kirchoff 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.

2. Oct 6, 2005

### Tom Mattson

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

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.

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