# RC Frequency Phase-Shift Calculation

Discussion in 'Homework Help' started by JDR04, Sep 17, 2012.

1. ### JDR04 Thread Starter Active Member

May 5, 2011
344
4
Hi Folks, revisiting this one.

I've attached the information I have on this question. What I don't understand is how the 50 and the 5 are derived in the formula. I think the 5 is derived from the fact that there are 5 wave forms in total with the circuit but am not sure.

I can easily apply the formula as it is but would like to understand what I am doing and why.

I think forum member WBahn would have an interest in this one as he previousely offered some wise advice to me.

Your help will be appreciated and thanks again......JDR04

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2. ### ecesoul New Member

Sep 8, 2012
8
0
f=1/(2 x pi x R x C x sqrt(6))
this become 50/RC..may be some rough practical approximation

5k x 0.05microFarad = 5 x .05 ? might be wrong

3. ### JDR04 Thread Starter Active Member

May 5, 2011
344
4
Might be,but I cant find any reference to it on the internet. My tutor is away as well so I cant get any help there either.Anyway thanks.-JDR04

4. ### t_n_k AAC Fanatic!

Mar 6, 2009
5,448
790
A detailed analysis of your oscillator is well established in the literature.

It can be shown after a good deal of algebra that

$f_{osc}=\frac{1}{2\pi R C \sqrt{6+4\frac{R_C}{R}}} \ Hz$

If [as in your case] Rc=R then

$f_{osc}=\frac{1}{2\pi RC \sqrt{10}}=\frac{0.0503}{RC} \ Hz$

if R is in kΩ and C is in uF then

$f_{osc}=\frac{50.03}{RC} \ Hz$

5. ### JDR04 Thread Starter Active Member

May 5, 2011
344
4
Thanks t n k. It's all way above my level at the moment but I'll go through it bit by bit and see if I can make sense of it.

Thanks for your time and input- JDR04

6. ### JDR04 Thread Starter Active Member

May 5, 2011
344
4
Sorry, I meant to ask t n k. So the formula given in the text is a short cut in this situation. In any other type of phase shift frequency calculation the proper formula to use is the one supplied by you in you post.

Am I understanding this properly so far? Thanks again - JDR04