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Mathematics 15 Online
OpenStudy (abb0t):

frequency response, bode plot

OpenStudy (abb0t):

@nubeer

OpenStudy (nubeer):

yes

OpenStudy (abb0t):

\( \LARGE G(s) = \frac{10}{s+10}\)

OpenStudy (nubeer):

umm yes so we would take 20log 10?

OpenStudy (abb0t):

its basically asking, how is |dw:1367183247579:dw| if you go on by changing the value of "S"

OpenStudy (abb0t):

\[\frac{ 10 }{ 10+j \omega } \]

OpenStudy (nubeer):

yes.

OpenStudy (abb0t):

but you might as well write that as \[\large \frac{ 10 }{ 10(1+\frac{ j \omega }{ 10 }) }\]

OpenStudy (nubeer):

umm yes..

OpenStudy (abb0t):

which is \[\frac{ 10 }{ 1+j \frac{ \omega }{ 10 } }\] and what would be the magnitude?

OpenStudy (nubeer):

hmm wouldn't that 10 in numerator would be cancelled out by the denominator one?

OpenStudy (abb0t):

one step at a time :) magnitude is: \[|G| = \frac{ 1 }{ \sqrt{1+\frac{ \omega ^2 }{ 10^2 }} }\]

OpenStudy (nubeer):

ok.. getting so far.

OpenStudy (abb0t):

when \( \omega\) is very very small, you know that \( \omega <<10\)

OpenStudy (abb0t):

and |G| will be tending to 1

OpenStudy (nubeer):

yes.

OpenStudy (abb0t):

and hence, 20log(|G|) = 0

OpenStudy (abb0t):

approximately 0 db

OpenStudy (nubeer):

yes makes sense.. so a straight horizontal line at 0 db?

OpenStudy (abb0t):

now let's take a look at when \( \omega >> 10\)

OpenStudy (abb0t):

calling \(\frac{\omega}{10}=x\) you can get \[\frac{ 1 }{ \sqrt{1+x^2} }\]

OpenStudy (abb0t):

but the \(x^2\) will be dominating under there.

OpenStudy (abb0t):

so you can approximate it to \(\huge|G| = \frac{1}{\frac{\omega}{10}}\)

OpenStudy (abb0t):

which is same thing as \(\huge \frac{10}{\omega}\)

OpenStudy (nubeer):

yes.

OpenStudy (abb0t):

|dw:1367184037343:dw|

OpenStudy (abb0t):

ok give me a minute for the next part im gonna try and cram it all lol. i was practicing my latex haha

OpenStudy (nubeer):

hahha no worries.

OpenStudy (abb0t):

when \(\omega\) is equal to 10 omega by 10 is equal to 1. so log of 1 = zero. if you increase the frequency, persay, by some fold, 10-fold at some other frequency, 2 \(10\times \omega_1\) = \(\omega_2\) . \(log_2(10 \omega)_1\) what value do u get? meaning, increasing the frequency 10 times from anywhere, you simply get \(log(10)+log(\omega_1\)

OpenStudy (abb0t):

log(10) = 1 and so you are basically adding 1 per frecqueyc. but in this example, omega is in the denominator, so you're actually subtracting 1.

OpenStudy (abb0t):

-log\((\omega)\)

OpenStudy (nubeer):

degree?

OpenStudy (abb0t):

|dw:1367184828381:dw|

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