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devil
02/05/13 2:19pm

Hi,

I want to calc the cutoff frequency of a System.

sys = s/(1000 + s)


For it I want to check were the 2. derivative of the amplitude is 0.

I tried to plot every step to find the mistake. But I don't know why it don't works!?

The 1. Plot is well. In the 2. and 3. nothing is plotted ... why?


ampl = Abs[sys /. {s -> 2*Pi*f*I}]


LogLogPlot[ampl, {f, 100, 1000}]
abl1 = D[ampl, f]
LogPlot[abl1, {f, 100, 1000}]
abl2 = D[abl1, f]
LogPlot[abl2, {f, 100, 1000}]

Solve[abl2 == 0 && f > 0, f]

I would be very thankful if you can help me!
Thanks

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Subject (listing for 'derivative of amplitude-frequency characteristic')
Author Date Posted
derivative of amplitude-frequency characteristic devil 02/05/13 2:19pm
Re: derivative of amplitude-frequency character... Bill Simpson 02/05/13 6:43pm
Re: Re: derivative of amplitude-frequency chara... devil 02/06/13 2:22pm
Re: Re: Re: derivative of amplitude-frequency c... Bill Simpson 02/06/13 8:25pm
Re: Re: Re: Re: derivative of amplitude-frequen... devil 02/07/13 1:08pm
Re: derivative of amplitude-frequency character... devil 02/20/13 07:16am
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