analogrf wrote on Apr 14th, 2011, 11:04am:Thanks indeed for the reply.
What i wanted to know was, if one can track which respective nodes are each of these coming from (now they are associated with the SS model nodes ! ) .
The PZ simulation is always performed on a small signal model. This small signal model can be one created by the simulator from the DC operating point of a circuit with non-zero DC biasing. Or it can be the small signal equivalent circuit entered into the simulator by the user. In either case, if the user manually derives a transfer function, then the user will find that , in general, the poles and zeros of that transfer function do not have a one-to-one correspondence to individual nodes of the circuit. The poles and zeros are, in general, functions of any of the elements in the circuit.
A pole or zero in radians per second is equal to the reciprocal of a time constant. For example, a simple RC time constant. The R can be between a pair of nodes in the circuit and the C can be between a different pair of nodes. In this example, then, their are 4 nodes which correspond to the pole or zero. And therefore, I think the question of tracking which node is associated with a pole or zero can only be answered by explaining that the question contains an incorrect assumption.
There are situations in which both the R and the C are connected between a node and AC ground, and there are situations where this is an appropriate approximation, but, it is not the general case.