# Homework Help: Transfer function for RC and RL circuits

1. Feb 16, 2014

### evol_w10lv

1. The problem statement, all variables and given/known data
I just want to understand, how to calculate transfer function.
Here is simple example:

2. Relevant equations

3. The attempt at a solution
But in this circuit I don't understand how to do it.

I have to find T and k as it is in preview. Which is the element for Vout in this circuit? Or what I shoud find first?

2. Feb 17, 2014

### Staff: Mentor

vout = (1/C). i2.dt

→ vout(s) = 1/(sC).i2(s)

where i2 is the current into the output capacitor, C2.

Now, find equations that allow you to substitute something for i2. Keep going, applying Kirchoff's Laws as you work towards the left until you have vout in terms of vin but no other unknowns.

3. Feb 17, 2014

### rude man

The impedance of a capacitor is 1/sC. So treat this network as impedances just as though the capacitors were resistors.

(This is per the fact that for a capacitor, i = C dv/dt or I = sCV so Z = V/I = 1/sC.)