Re: Error with tf(): # of poles < # of zeros

[Axax]

Il giorno gio, 25/03/2010 alle 22.33 -0400, Doug Stewart ha scritto:


> Yes there is.
> 
> Try doing the inverse Laplace transform on s
> 
> inverse of (1/s)  is a step function
> inverse of  (1) is an impulse function
> inverse of (s) is  ??? Well it is the derivative of the impulse
> function ---- which is a positive going impulse and a negative going
> impulse at the same time.  
> Have fun doing the inverse of s^2   :-)

Oh thanks, I haven't think to follow this way :)
> 
> So Octave and math in general needs the numerator to be of the same or
> less order of polynomials.
> 
> If you are working in control theory and you say "yes but I can build
> the circuit and it works  -- so why can't we simulate the circuit that
> I built"   --- then the answer is that there are some high frequency
> poles on your opamp that you are ignoring. So just add some high
> frequency poles and keep your DC gain the same. and it will work.

hummm... I like this! Fits more the reality!
> 
> 1000
> --------
> s + 1000
> 
> 
> My students run into this every year :-)
> Doug Stewart
> 
> 
Thank you!

Axel
>