# Simple inverse Laplace using PFE not so simple?

1. Jun 17, 2015

### jrive

Hello,

When evaluating the step response of a circuit, the resulting Laplace representation is:
$\frac{I_{pd}}{s^2 C1 R1}$

If I look this up on a table of Laplace Transforms, this results in $\frac{I_{pd}*t}{C1 R1}$.

However, I'm struggling to solve this via partial fraction expansion--is there a special trick or step I need to take that would enable me to arrive at the same solution? I don't see where I'm going wrong.

Thanks!

Last edited: Jun 17, 2015
2. Jun 17, 2015

### Hesch

I cannot read this. please write it in another way. It seems to be something like:

IR / (C1*R1) * ( 1 / s ) which is simply a step function.

3. Jun 17, 2015

### jrive

Sorry, my latex is rusty and i can't figure out how to make it work.
So, here it is directly Ipd/(R1*C1*s^2).

In time domain, this results in t*Ipd/(R1*C1). My problem is I can't seem to get there via partial fraction expansion....

Last edited: Jun 17, 2015
4. Jun 18, 2015

### jrive

Never mind, i figured it out....