raja.cedt wrote on May 12th, 2009, 8:11pm:hi but if nulling resistor is there then you can distribute whatever voltage you want according to kvl remaining voltage will come across Rz.
Hi Rajasekhar,
Thanks for your clarifications. However I still disagree about the third pole: having a third degree of freedom (which is true) does not necessarily mean you have a a three pole system. Actually such extra degree of freedom is the one that allows to cancel the RHP by means of the nulling resistor. In other words the third degree of freedom is a capacitor in
series with the signal, i.e. is places a zero, while the other two nodes are shunting the signal, thus generate poles.
As an example of a system with two degree of freedoms -
but one pole - just consider the passive filter attached. The transfer function shows one pole and one zero, and clearly two degrees of freedom.
Going back to the nulling resistor case, for me the effect of the nulling resistor is two-fold:
1) Affects the location of the first and second poles
2) Brings the zero from the RHP to the LHP (this is the third degree of freedom that does not exist without Rz)
I might be missing something but I do not see how the third poles is generated here.
Regards
Tosei