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Old 02-02-2008, 01:45 AM
gokul_s1
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Default Circuit with two poles?

I am looking for a circuit whose transfer function (V(z)/I(z)) comprise
just two poles. Is it possible to build such a circuit using just RL
elements?

Thanks for your help

Gokul
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  #2 (permalink)  
Old 02-02-2008, 02:41 AM
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Default Re: Circuit with two poles?

On Feb 2, 2:45 pm, "gokul_s1" <[email protected]> wrote:
> I am looking for a circuit whose transfer function (V(z)/I(z)) comprises
> just two poles. Is it possible to build such a circuit using just RLC
> elements?
>
> Thanks for your help
>
> Gokul


Yes - take the output from the capacitor. There are of course three
conditions depending on whether you want
underdamped,overdamped,critical damped. Also watch the impedance if
you are sampling the output or connecting it to something else.

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Old 02-02-2008, 02:55 AM
Tim Wescott
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Default Re: Circuit with two poles?

On Fri, 01 Feb 2008 19:45:23 -0600, gokul_s1 wrote:

> I am looking for a circuit whose transfer function (V(z)/I(z)) comprises
> just two poles. Is it possible to build such a circuit using just RLC
> elements?
>
> Thanks for your help
>
> Gokul


Theoretically, how about this:


o---UUUU---o-----o
|
===
|
o----------o-----o

Practically, any real circuit will have an infinite number of poles and
zeros; at lower frequencies you can very effectively pretend that the
circuit matches theory exactly.

--
Tim Wescott
Control systems and communications consulting
http://www.wescottdesign.com

Need to learn how to apply control theory in your embedded system?
"Applied Control Theory for Embedded Systems" by Tim Wescott
Elsevier/Newnes, http://www.wescottdesign.com/actfes/actfes.html
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  #4 (permalink)  
Old 02-02-2008, 07:23 AM
gokul_s1
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Default Re: Circuit with two poles?

Why does a practical circuit have infinite poles and zeros? Is it becaus
the circuit elements are actually distributed and not lumped as they ar
usually assumed to be?

-Gokul

>On Fri, 01 Feb 2008 19:45:23 -0600, gokul_s1 wrote:
>
>> I am looking for a circuit whose transfer function (V(z)/I(z)

comprises
>> just two poles. Is it possible to build such a circuit using just RLC
>> elements?
>>
>> Thanks for your help
>>
>> Gokul

>
>Theoretically, how about this:
>
>
> o---UUUU---o-----o
> |
> ===
> |
> o----------o-----o
>
>Practically, any real circuit will have an infinite number of poles and
>zeros; at lower frequencies you can very effectively pretend that the
>circuit matches theory exactly.
>
>--
>Tim Wescott
>Control systems and communications consulting
>http://www.wescottdesign.com
>
>Need to learn how to apply control theory in your embedded system?
>"Applied Control Theory for Embedded Systems" by Tim Wescott
>Elsevier/Newnes, http://www.wescottdesign.com/actfes/actfes.html
>

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  #5 (permalink)  
Old 02-02-2008, 05:34 PM
Tim Wescott
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Default Re: Circuit with two poles?

On Sat, 02 Feb 2008 01:23:20 -0600, gokul_s1 wrote:
(top posting fixed)
>>On Fri, 01 Feb 2008 19:45:23 -0600, gokul_s1 wrote:
>>
>>> I am looking for a circuit whose transfer function (V(z)/I(z))

> comprises
>>> just two poles. Is it possible to build such a circuit using just RLC
>>> elements?
>>>
>>> Thanks for your help
>>>
>>> Gokul

>>
>>Theoretically, how about this:
>>
>>
>> o---UUUU---o-----o
>> |
>> ===
>> |
>> o----------o-----o
>>
>>Practically, any real circuit will have an infinite number of poles and
>>zeros; at lower frequencies you can very effectively pretend that the
>>circuit matches theory exactly.
>>
>>--
>>Tim Wescott
>>Control systems and communications consulting
>>http://www.wescottdesign.com
>>
>>Need to learn how to apply control theory in your embedded system?
>>"Applied Control Theory for Embedded Systems" by Tim Wescott
>>Elsevier/Newnes, http://www.wescottdesign.com/actfes/actfes.html
>>

> Why does a practical circuit have infinite poles and zeros? Is it
> because the circuit elements are actually distributed and not lumped as
> they are usually assumed to be?
>
> -Gokul
>

More or less. You may want to consider the lead-lead capacitance of your
inductor as another lumped element, and the lead inductance of your
capacitor as a lumped element, but ultimately you get down to the fact
that the elements are distributed.

Sometimes you can get by with assuming that the elements are perfect, or
perfect with just one or two parasitic elements. Sometimes you just have
to accept that their distributed -- it all depends on the physical
construction of your circuit, your needs, and the frequency that it's
operating at.

--
Tim Wescott
Control systems and communications consulting
http://www.wescottdesign.com

Need to learn how to apply control theory in your embedded system?
"Applied Control Theory for Embedded Systems" by Tim Wescott
Elsevier/Newnes, http://www.wescottdesign.com/actfes/actfes.html
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