# 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 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.

Related Engineering and Comp Sci Homework Help News on Phys.org

#### Tom Mattson

Staff Emeritus
Gold Member

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.

### Physics Forums Values

We Value Quality
• Topics based on mainstream science
• Proper English grammar and spelling
We Value Civility
• Positive and compassionate attitudes
• Patience while debating
We Value Productivity
• Disciplined to remain on-topic
• Recognition of own weaknesses
• Solo and co-op problem solving