# Filter Identification

Discussion in 'Homework Help' started by mcdignan, Nov 14, 2007.

1. ### mcdignan Thread Starter New Member

Nov 14, 2007
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Is there any way to determine what type of filter you have without deriving the transfer function from a provided RCL circuit sketch? As an example i am dealing with a homework problem that gives three circuit filters and wants me to identify what type they are. I know how to get the transfer function for them and then roughly sketch a Bode plot but i feel that there must be an easier way to do this. Maybe by looking at each circuit element and whether they are in series or parallel with one another....

2. ### beenthere Retired Moderator

Apr 20, 2004
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Think about the response of a capacitor and then an inductor to frequency. Look at the arrangement of the C and L elements in the various circuits in that light, and see what it suggests to you.

3. ### Management Active Member

Sep 18, 2007
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Just to play off what beenthere said, think about what happens at low frequencies and also what happens at extremely high frequencies and that will, along with the placement of components, what type of filter you are looking at.

4. ### Distort10n Active Member

Dec 25, 2006
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Yes, and infact many engineers do this. There are three types:

1) Purely theoretical. 'Show me the math' type of guys. They will astound you with their ability to solve TF's in their head. Then will will explain the circuit to you.

2) Purley practical. Cannot or will not explain a circuit using equations. They will think of how elements respond to voltage, current, frequency, etc. A more 'inuitive' or conceptual feel for the circuit.

3) A little bit of both. I am like this.