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types of filters

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niga

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Hello There

I really need some help in this.I am reading on passive filters.There are 5 types-
1.low pass
2.high pass
3.bandpass
4.bandreject
5.resonant

is this understanding correct?


i am confused coz i read some papers which say that

1. band pass and band reject are resonant filters.IS it right?

2.some papers say that the series connection of highpass and lowpass is called BANDPASS FILTER and the parallel connection of highpass and lowpass is BANDREJECT or BANDSTOP FILTER.

While some papers say that BANDPASS and BANDSTOP have both series and parallel connection of highpass and lowpass.

I am totally confused. :shock:

Please do help me.Thankyou so much.
 
niga said:
1. band pass and band reject are resonant filters. IS it right?
Only if their bandwidth is narrow. A 20Hz to 20kHz audio bandpass or reject filter is definately not resonant.

2. some papers say that the series connection of highpass and lowpass is called BANDPASS FILTER and the parallel connection of highpass and lowpass is BANDREJECT or BANDSTOP FILTER.
You never connect filters in parallel. If you connect a lowpass filter and a highpass filter in series or add the two together, the output is a bandpass filter.
If you subtract a lowpass filter and a highpass filter, the output is a band-reject filter.

While some papers say that BANDPASS and BANDSTOP have both series and parallel connection of highpass and lowpass.
You are probably confusing a series and parallel LC filter type, with putting filters in series or in parallel. You are probably also confusing putting a series LC filter in series with a load, or putting a series resistor feeding a parallel LC filter to ground, to make a bandpass filter.
Likewise, putting a parallel LC filter in series with a load, or putting a series resistor feeding a series LC filter to ground makes a band reject filter.

Understand? :lol:
 
Thanx unclescrooge for ur reply.
But i din really understand the last part.

i got this info from allaboutcircuits.com

and www.tpub.com/content/neets/14181

what do u mean by there is no parallel connection of Highpass and Lowpass?Why not?But i read in Floyd too that conting these in parallel gives bandstop.What i am really confused abt is

Okay...how do u make a bandstop?subtracting HP and LP?

I am confused as ever.
:(
 
Hi Niga,
No wonder you are confused, your posted document is plainly wrong!
A) Low frequencies pass through an inductor. Correct.

B) Low frequencies pass to ground through a capacitor. Wrong.
High frequencies pass to ground through a capacitor.

C) High frequencies pass to ground through a capacitor. Correct.
High frequencies pass through an inductor. Wrong.
Low frequencies pass through an inductor.

The output of a lowpass filter is high frequencies. Wrong.
The output of a lowpass filter is low frequencies.
 

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I tot that was wrong tooo thanx Uncle Scrooge for the help.but i am still not sure abt the

You never connect filters in parallel.
coz

some papers say that the series connection of highpass and lowpass is called BANDPASS FILTER and the parallel connection of highpass and lowpass is BANDREJECT or BANDSTOP FILTER.
While some papers say that BANDPASS and BANDSTOP have both series and parallel connection of highpass and lowpass.



i hope u got what my problem is abt.
let me make it simpler

IS BANDPASS filter the series (ONLY)connt of HP and LP ?
and
Is BANDSTOP filter the parallel (only) connt of HP and LP ?

OR is it like this


bandstop
/ \
series parallel


bandpass
/ \
series parallel


Thankyou.
 
thanx for ur respone Fried,
I am to understand that series and parallel confugirations exists in both BP and BS filters.
 
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