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