TRANSIENT command

Syntax

Transient start stop stepsize {options ...}
Transient stepsize stop start {options ...}

Purpose

Performs a nonlinear time domain (transient) analysis.

Comments

The nodes to look at must have been previously selected by the Print or Plot command.

Three parameters are normally needed for a Transient analysis: start time, stop time and step size, in this order. The SPICE order (step size, stop, start) is also acceptable. An optional fourth parameter is the maximum internal time step.

If all of these are omitted, the simulation will continue from where the most recent one left off, with the same step size, unless the circuit topology has been changed. It will run for the same length of time as the previous run.

Do not use a step size too large as this will result in errors in the results. If you suspect that the results are not accurate, try a larger argument to `Skip'. This will force a smaller internal step size. If the results are close to the same, they can be trusted. If not, try a still larger `Skip' argument until they appear to match close enough.

The most obvious error of this type is aliasing. You must select sample frequency at least twice the highest signal frequency that exists anywhere in the circuit. This frequency can be very high, when you use the default step function as input. The signal generator does not have any filtering.

Options

> file

Send results of analysis to file.

» file

Append results to file.

Cold

Zero initial conditions. Cold start from power-up.

DTMIn = x

Minimum time step. (Default = from options) The smallest internal time step in transient analysis. The transient command dtmin option and the dtratio option override it if it is bigger.

DTRatio = x

The ratio between minimum and maximum time step. (Default = from options).

NOPlot

Suppress plotting.

PLot

Graphic output, when plotting is otherwise off.

Quiet

Suppress console output.

Skip count

Force at least count simulation steps for each one displayed. If the output is a table or ASCII plot, the extra steps are hidden.

TEmperature degrees

Temperature, degrees C.

TRace n

Show extended information during solution. Must be followed by one of the following:

Off

No extended trace information (default, override .opt)

Warnings

Show extended warnings

Alltime

Show all accepted internal time steps.

Rejected

Show all internal time steps including rejected steps.

Iterations

Show every iteration.

Verbose

Show extended diagnostics.

UIC

Use initial conditions. Use the values specified with the IC = options on the various elements.

Examples

transient 0 100u 10n

Start at time 0, stop after 100 micro-seconds. Simulate using 10 nanosecond steps.

transient

No parameters mean to continue from the last run. In this case it means to step from 100 us to 200 us in 10 ns steps. (The same step size and run length, but offset to start where the last one stopped.

transient skip 10

Do 10 extra steps internally for every step that would be done otherwise. In this case it means to internally step at 1 nanosecond. If the output is in tabular form, the extra steps are hidden.

transient 0

Start over at time = 0. Keep the same step size and run length.

transient cold

Zero initial conditions. This will show the power-on transient.

transient >arun

Save the results of this run in the file arun.