% op.tex  94.07.29
% man commands op .
% Copyright 1983-1992   Albert Davis
%------------------------------------------------------------------------
\section{{\tt OP} command}
\index{op command}
\index{operating point}
\index{bias analysis}
\index{nonlinear bias analysis}
\index{temperature sweep}
\index{quiescent conditions}
%------------------------------------------------------------------------
\subsection{Syntax}
\begin{verse}
{\tt OP} {\it start stop stepsize} \{{\it options} ...\}
\end{verse}
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\subsection{Purpose}

Performs a nonlinear DC steady state analysis, with no input.  If a
temperature range is given, it sweeps the temperature.
%------------------------------------------------------------------------
\subsection{Comments}

There are substantial extensions beyond the capabilities of the SPICE {\tt
op} command.

If there are numeric arguments, they represent a temperature sweep.  They are
the start and stop temperatures in degrees Celsius, and the step size, in
order.  They are saved between commands, so no arguments will repeat the
previous sweep.

This command will use the {\tt op} probe set, instead of automatically
printing all nodes and source currents, so you must do "{\tt print
op} ...." before running op.  We did it this way because we believe
that printing everything all the time is usually unnecessary clutter.
All of the information available from SPICE and more is available
here.  See the {\tt print} command and the device descriptions for
more details.

A single parameter represents a single temperature.  Two parameters instruct
the computer to analyze for those two points only.

This command also sets up the quiescent point for subsequent {\tt AC}
analysis.  It is necessary to do this for nonlinear circuits.  The last step
in the sweep determines the quiescent point for the AC analysis.
%------------------------------------------------------------------------
\subsection{Options}

\begin{description}

\item[{\tt *} {\it multiplier}] Log sweep.  Multiply the
{\em absolute} temperature by {\it multiplier} to get the
next step.  The fact that it is offset to absolute zero
may make the step sizes look strange.

\item[{\tt >} {\it file}] Send results of analysis to {\it file}.

\item[{\tt >>} {\it file}] Append results to {\it file}.

%%%\item[{\tt ACMAx}] Use worst case max values, per last
%%%{\tt AC} analysis.

%%%\item[{\tt ACMIn}] Use worst case min values, per last
%%%{\tt AC} analysis.

\item[{\tt BY} {\it stepsize}] Linear sweep.  Add {\it
stepsize} to get the next step.

\item[{\tt Continue}] Use the last step of a {\tt OP},
{\tt DC} or {\tt Transient} analysis as the first guess.

%%%\item[{\tt DCMAx}] Use worst case max values, per last
%%%{\tt DC} or {\tt OP} analysis.

%%%\item[{\tt DCMIn}] Use worst case min values, per last
%%%{\tt DC} or {\tt OP} analysis.

\item[{\tt Input} {\it volts}] Apply {\it volts} input to
the circuit, instead of zero.

%%%\item[{\tt LAg}] Use worst case values, for lagging phase,
%%%per {\tt AC} analysis.

%%%\item[{\tt LEad}] Use worst case values, for leading
%%%phase, per {\tt AC} analysis.

\item[{\tt LOop}] Repeat the sweep, backwards.

%%%\item[{\tt MAx}] Use worst case max values, per same type
%%%({\tt OP} or {\tt DC}) analysis.  (Same as {\tt DCMAx},
%%%here.)

%%%\item[{\tt MIn}] Use worst case min values, per same type
%%%({\tt OP} or {\tt DC}) analysis.  (Same as {\tt DCMIn},
%%%here.)

%%%\item[{\tt MCarlo} {\it trials}] Monte-Carlo analysis.
%%%Simulate {\it trials} circuits; compile statistics.  Hide
%%%individual trials.

\item[{\tt PLot}] Graphic output, when plotting is
normally off.

\item[{\tt Print}] Send results to printer.

\item[{\tt Quiet}] Suppress console output.

%%%\item[{\tt RAndom} {\it trials}] Simulate {\it trials}
%%%circuits using random values.

\item[{\tt REverse}] Sweep in the opposite direction.

\item[{\tt TAble}] Tabular output. Override default plot.

\item[{\tt TEmperature} {\it degrees}] Temperature,
degrees C.  Override the sweep.

\item[{\tt TImes} {\it multiplier}] Log sweep.  Multiply
the {\bf absolute} temperature by {\it multiplier} to get
the next step.

\item[{\tt TRace} {\it n}] Show extended information during solution.
\begin{description}
\item[4] Show every iteration.
\item[5] Show extended diagnostics.
\end{description}

%%%\item[{\tt WOrstcase} {\it probe}] Worst case analysis, at
%%%{\it probe}.

\end{description}
%------------------------------------------------------------------------
\subsection{Examples}

\begin{description}

\item[{\tt op 27}] Do a DC operating point simulation at temperature 27
degrees Celsius.

\item[{\tt op -50 200 25}] Sweep the temperature from -50 to 200 in 25
degree steps.  Do a DC operating point simulation at each step.

\item[{\tt op}] With no parameters, it uses the same ones as the last time.
In this case, from -50 to 200 in 25 degree steps.

\item[{\tt op 200 -50 -25}] You can sweep downward, by asking for a negative
increment.

\item[{\tt op Input 2.3}] Apply an input to the circuit of 2.3 volts.  This
overrides the default of no input.

\item[{\tt op TEmperature 75}] Simulate at 75 degrees, this time.  This isn't
remembered for next time.

\item[{\tt op}] Since the last time used the {\tt TEmperature} option, go
back one more to find what the sweep parameters were.  In this case, downward
from 200 to -50 in 25 degree steps.  (Because we did it 3 commands ago.)

\end{description}
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%------------------------------------------------------------------------
