# Z Diagram of Low Pass Filter

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• Posted on I am to draw an impedance diagram of a low pass filter comprising resistor &
capacitor, and to indicate the phase angle. I am in dispute with teacher on
the phase angle.
Is the phase angle found by:
1) -arctan(wRC)
or
2) -arctan(Xc/R)
Appreciate if someone could advise which one of the above is correct.

TIA Re: Z Diagram of Low Pass Filter #1 gets the nod. Which did you pick?
http://www.phys.unsw.edu.au/~jw/RCfilters.html Re: Z Diagram of Low Pass Filter

Thanks for that, teach is right! I picked #2  Re: Z Diagram of Low Pass Filter that is just general current in the circuit. Re: Z Diagram of Low Pass Filter

"BIGEYE" **    Xc  =  1/ wC

so    Xc/R  =  1/ wRC

and   R/Xc  =  wRC

When C is small, Xc is large and in case of a LPF the phase angle ( or phase
shift ) approaches zero when C is small.

Only formula 1 give zero phase for small C.

......    Phil

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