The pole-zero analysis computes the poles and/or zeros in the small-signal ac transfer function. The program first computes the dc operating point and then determines the linearized, small-signal models for all the nonlinear devices in the circuit. This circuit is then used to find the poles and zeros of the transfer function.

Two types of transfer functions are allowed: one of the form (output voltage)/(input voltage) and the other of the form (output voltage)/(input current). These two types of transfer functions cover all the cases and one can find the poles/zeros of functions like input/output impedance and voltage gain. The input and output ports are specified as two pairs of nodes.

The pole-zero analysis works with resistors, capacitors, inductors, linear-controlled sources, independent sources, BJTs, MOSFETs, JFETs and diodes. Transmission lines are not supported.

The method used in the analysis is a sub-optimal numerical search. For large circuits it may take a considerable time or fail to find all poles and zeros. For some circuits, the method becomes "lost" and finds an excessive number of poles or zeros.


Enter a brief description of the type of analysis. The text entered is the title of the document in which the simulation results will be stored.

Input Node

The positive input node and the reference node for the input of the circuit.

Output Node

The positive output node and the reference node for the output of the circuit.

Type of signal

Defines the type of ac small-signal transfer function to be used for the circuit when calculating the poles and/or zeros. There are two types available:

Analysis Type

Choose to find all poles that satisfy the transfer function for the circuit, all zeros, or both Poles and Zeros. This feature is provided mainly because if there is a nonconvergence in finding poles or zeros, then, at least the other can be found.


Specify the temperature at which the simulation will be performed.


Click on this button to activate the dialog box in which to set the options of the simulator. The options set are only valid for the current analysis and replace those defined in the general tab of the simulator options.

See also