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Bandpass Filter Respone

09/27/2014 10:03 PM

can someone help me answer this quiz? http://www.eeweb.com/electronics-quiz/filter-response

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#1

Re: Bandpass Filter Respone

09/27/2014 10:09 PM

Visualize in your mind *how* the resistors are "connected" at the two frequency states:

0 Hz (DC, low-frequency) where capacitors are "opens", so the resistors are NOT connected between input and output.

∞ Hz (high-frequency) where capacitors are "shorts", so just the resistors are left in the signal patch between input and output.

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#2
In reply to #1

Re: Bandpass Filter Respone

09/27/2014 10:15 PM

click first the link in order to see the question.

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#3

Re: Bandpass Filter Respone

09/27/2014 11:24 PM

I have found a primer for you that explains this circuit in detail....It is a capacitive band-pass filter that filters both high and low frequencies outside a specific range....

http://www.ibiblio.org/kuphaldt/electricCircuits/AC/AC_8.html

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#4

Re: Bandpass Filter Respone

09/28/2014 6:11 AM

Just a short comment to the above link:

One should keep in mind that - as outlined in the document - a simple multiplication of both transfer functions - lowpass and highpass - is allowed only if the second part (highpass) does not considerably load the first part. In the document, this is approximately accomplished using the scaling factor 10. However, the result therefore is not error-free.

Why not applying KVL and KCL for calculating the correct transfer function (that means: not simply by separate low- and highpass).

Remark: The shown circuit is the "worst" bandpass you can ever realize. It has a quality factor below Q=Fo/BW=0.5 (Bandwidth BW>2*Fo) .

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#5
In reply to #4

Re: Bandpass Filter Respone

09/28/2014 9:59 AM

A good answer but I suspect an answer that is not helpful for the OP.

The OP recognizes that this is a band pass filter. Thus the first part of the quiz is identified.

I'm puzzled that the OP cannot complete the second quiz part of constructing a net list for a simulator. There are many GUI programs that can construct a net list from a schematic but it is good to understand the syntax of net lists so one can be sure that the simulator is working on the correct topology.

I would expect a student in an academic class would be able to construct a transfer function from this schematic. Only once this can be demonstrated would I show them the standard form of a one pole band pass filter so they could identify the Q of the circuit and how it relates to bandwith and how to identify the peak band pass frequency.

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#6
In reply to #5

Re: Bandpass Filter Respone

09/28/2014 10:16 AM

Since the answer is readily available, on the referenced website, to kristine14, I'm guessing that she is requesting some help understanding the concept and function of electronic band pass filters.

I'm also guessing that she's 14 years old, maybe.

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#7
In reply to #6

Re: Bandpass Filter Respone

09/28/2014 10:42 AM

Agreed.

I should have been more explicit to kristine14 in my request. If she identifies a little more clearly what she needs help in understanding, I'll do my best to help.

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#8

Re: Bandpass Filter Respone

09/28/2014 11:21 AM

Just go to the link you referenced and click on "Show Answer"...it's all there I believe.

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#9

Re: Bandpass Filter Respone

05/18/2021 3:11 PM

The diagrams in the EEWeb, referenced by Kristine14, leave out the labelling of the "source - C1 - R2" interconnection/node as "0" [zero], which is not helpful to the beginner.

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