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##

`.pz` Line

The pole-zero analysis portion of *WRspice* 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.

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 and Josephson junctions are not
supported.

- General Form:

`.pz `*node1 node2 node3 node4* cur|vol pol|zer|pz

- Examples:

`.pz 1 0 3 0 cur pol
`

.pz 2 3 5 0 vol zer

.pz 4 1 4 1 cur pz

The keyword `cur` stands for a transfer function of the type
(output voltage)/(input current) while `vol` stands for a transfer
function of the type (output voltage)/(input voltage). The keyword
`pol` stands for pole analysis only, `zer` for zero analysis
only and `pz` for both. This feature is provided mainly because
if there is a nonconvergence in finding poles or zeros, then, at least
the other can be found. Finally, *node1* and *node2* are
the two input nodes and *node3* and *node4* are the two
output nodes. Thus, there is complete freedom regarding the output
and input ports and the type of transfer function.

In interactive mode, the **pz** command, which takes the same
arguments as the `.pz` line, can be used to initiate pole-zero
analysis.

Pole-zero analysis is not available if Josephson junctions are
included in the circuit.

** Next:** .sens Line
** Up:** Analysis Specification
** Previous:** .op Line
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Stephen R. Whiteley
2021-01-27