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ywcheung

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how to prove and extend the transfer function of the LPF,HPF,BPF and BSF??
 

what do you want? circuit or simulation?
 

find the zeros and poles from these equations?
 

You should be able to evaluate the equations and plot them. Alternately, find the roots of the numerator and denominator and use the Bode straight line approximation graphs.
 

um.....i want to know ....how come of this equation
 

if i understand what u want is how to diffreniate between diff. types ,for that by simple qualitative analysis is putting the s=0 for low frequency and s=inf for high freq.

for example:
1-LPF: s=0 gives a constant while s=infinity gives zero which is how a LPF acts.
2-HPF: s=0 gives zero while s=inf. gives constant (i.e. HPF)
3-BPF: s=0 gives zero also s=inf gives zero which means band pass.
4-BSF: s=0 gives constant and s=inf gives constant which means band stop.
 

All analog continious time filters have a transfert function that can be written as N(s)/D(s)
where N(s) the numerator is a polynome of degree n
D(s) the denominator is a polynome of degree p
s the laplace variable
and real filter have p > or = n
in reality a fiter is defined by a differential equation betweet input and output ( due to kirschoff equations)
You need some maths to transpose this differential equation into a transfer function with laplace transform

hope i helped you
 
You can plot amplitude response with some mathematical program like mathcad...
 
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