First of all, hi everyone. I decided to post questions because I started using wolfram mathematica just 1 day ago.

f(U)= IS (e^U/(n UT)-1) where UT is equal to 26 and IS equal to 10^-12

I tried to Plot the function on 4 different n values where n∈{3,6,9,12}

The problem with my graph is whenever I change the range I get different results. I checked if I'm getting correct results via desmos but not at all!

Here's what I used:

IS = 10^-12;
UT = 26;
nValues = {3, 6, 9, 12};
Plot[Table[IS (E^(U/(n UT)) - 1), {n, nValues}], {U, -200, 10000}]

{U,-200,10000} the graphs are changing whenever I change the range where all 4 different graphs should start to go up exponentially at an exact value. For instance when I change the range {U,-200,100} graphs going up exponentially very soon where the first one when n=3 it should be around U=2000 also having values different than 0 at the third region when I constrain the range? I know it is not true and I also do not want to constrain the range where all the graphs would look correct. What should I do?
What am I missing here?

Thank you for all in advance.