# S domain analysis help.

1. Mar 21, 2006

### seang

I have a homework problem that goes something like this: There's a circuit, A capacitor in parallel with a resistor, and those two are in series with another resistor. The values of the resistors are given, but the capacitor's is not. Then its given that Z(s) of the circuit equals some rational function. How do I find the value of the capacitor?

I've tried finding Z(s) of the circuit in terms of C and s, and then setting it equal to the given Z(s), but to no avail.

2. Mar 22, 2006

### Staff: Mentor

Homework problems should be posted in the homework forums, but I'll still try to give you a hint here. You need to write the Z(s) for the circuit, and equate that to the Z(s) given in order to figure out the C (I guess you know that part already).

To write the Z(s) for the circuit, just write it out like all the components were resistors, but use the appropriate Z(s) for each component. Like for the R, Z(s)=R. And if you had an inductor, Z(s)=sL. What is Z(s) for the capacitor? Then just use parallel and series combination rules for Z(s) to come up with the overall Z(s) for the circuit.