# Derive The Transfer Function from First Principles

All,

I need help deriving the Transfer Function of this circuit from first principles. http://i66.tinypic.com/24v3z9s.jpg

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anorlunda
Staff Emeritus
Do you consider Ohm's Law first principle ?

Do you consider Ohm's Law first principle ?
Yes

anorlunda
Staff Emeritus
Ok, have you learned about basic circuit analysis, series and parallel combinations?

If this is homework, it should be posted in the homework forum and use the template.

In short, No. No intro of circuit analysis and parallel/series combinations. Basically given this with one previous example and told to go figure it out. This is for a course in Signal Analysis.

Thanks Anorlunda, I will post it there.

analogdesign
Simplest way to attack this (i.e. how I would attack a similar problem at work).

1. Replace all devices with a general impedance (call it, for example, Z, so R1 = Z1, R2 = Z2, L = Z3, C = Z4.)
2. Solve the now trivial three-node voltage divider problem using KCL.
3. Replace all the Zs with their actual impedences (e.g. Z1 = R1, Z2 = R2, Z3 = sL, Z4 = 1/sC)
4. Simplify the expression and you're done!

anorlunda
Staff Emeritus
That's not nice for the teacher to give you that problem without the proper background.

If you are only interested in this problem, use @analogdesign 's advice in post #6. But basic circuits is something you'll surely need in your career. It is worth your time to learn it. A very effective and fast way to learn is using Khan Academy. It takes less than 5 hours there to learn a whole basic circuits course.