Since you have mentioned matlab for the bode plot, all you have to do is specify the transfer function and the 'bode' function will automatically calculte the magnitude and phase plots for you! From the bode plot you can infer the following properties.
The dominant pole occurs at the same location for both 1/(s-1) and 1/(s+1) in the magnitude plot. Magnitude is always the absolute value. hence it always occurs in the same location. The most important consideration is what are you trying to infer from the bode plot.
The presence of RHP pole reduces the phase margin of the system considerable. The phase plots give an important indication for this.
and complex conjugate poles cause the peaking behavior in the magnitude plots.
I hope i got your question right. Plotting the bode for the 2 systems will give u the same magnitude but different phase plots!
Well, i think you are getting confused with this particular example. even in this the 1st pole location is s+1 =0 and the second pole is not taken from the imaginary part of -0.5+/-j20. Use the pole(tf) and it'll give you the exact location of the poles. then using the abs(pole(tf)), you will get the exact pole locations on the bode plot!.
I guess its because of the example transfer function which is causing the problem.
Try the following tf (1/(s+2)(s^2+3s+17)).. just some random tf i have used. Now when you check the pole locations it will give u a better idea!
A simple way to explain the phase response would be as follows :
1. A dominant pole / zero always adds +/- 90 degrees to the phase plot depending on whether its a pole or a zero!
2. Coming to the complex-conjugate poles x+jy will add a phase tan-1(y/x) (complex algebra) to the phase plot depending on the signs of the complex conjugate poles.
You can verify this in the phase plots. Again this is a very crude way of putting things in perspective.
Hope what i made sense. IF others can verify what i just said!
I will play with matlab to confirm your 2nd point.
Speaking of dominant pole/zero, without doing small-signall, with some effort one can probably associate a particular node a circuit (opamp) with a dominant pole. However, intuitively, how to tell whether that pole is real, complex, right half plane, left half plane, etc ? Also, how to spot a (dominant) zero ?
Speaking of dominant pole/zero, without doing small-signall, with some effort one can probably associate a particular node a circuit (opamp) with a dominant pole. However, intuitively, how to tell whether that pole is real, complex, right half plane, left half plane, etc ? Also, how to spot a (dominant) zero ?
What do you mean with "intuitively"? Based on a known circuit diagram? Based on a known transfer function or on the step response in the time domain?
Why open loop? This is necessary only to determine either an appropriate feedback factor Hf or the phase margin (if Hf is fixed) after closing the loop. Up to now, I was of the opinion that you are interested in closed-loop pole location.
And what is the need to "tie these poles/zeros" to corresponding circuit nodes? Because of circuit modifications?
I must confess, the background behind your questions is not clear to me.
As far as stability is concerned: Are you familiar with Nyquist's stability criterion? This is important in the mentioned context.
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