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<html>
<body>
<h1> 12_bjt_amp_ac: pinout with spice/portmap </h1>
<h2> Scope </h2>
<p>
In this simulation we are going to look at a single-transistor amplifier
in frequency domain to verify how it amplifies a sine waves. Compared to
the <a href="10_bjt_amp_tr.html">trans variant</a> the only difference is
how we specify the transistor pinout and what spice commands we use for the
AC simulatuin
<h2> The schematics </h2>
<p>
Largely the same as <a href="10_bjt_amp_tr.html">trans variant</a>.
<p>
<center>
<a href="12_bjt_amp_ac.rs"><img src="10_bjt_amp_tr.svg" width=600px></a>
<br>Click the image to get the sch-rnd sheet; NOTE: the actual value of V1
has been changed from SINE() to a dc/ac combo.</center>
<p>
<h2> Preparing for simulation </h2>
<h3> Q1 </h3>
<p>
This example demonstrates using spice/portmap to set the pinout: the
stock spice/pinnum attributes has been manually removed from Q1 terminals and
a portmap attribute, array type, added to the Q1 symbol. The portmap is:
<pre>
{C->spice/pinnum=1}
{B->spice/pinnum=2}
{E->spice/pinnum=3}
</pre>
<p>
Since the attribute is called spice/portmap, it does not interfere with
the normal portmap attribute (installed by devmap in our example) and it
affects the spice workflow only.
<h3> V1 </h3>
<p>
V1 is generating the input sine wave on the <i>in</I> network.
The simulator will reconfigure it while sweeping the frequency for the
ac analysis.
<h3> V2 </h3>
<p>
V2 is an 5V DC power supply for Vcc:
<pre>
dc 5
</pre>
<h3> Raw spice commands </h3>
<p>
It contains the following script:
<pre>
ac dec 10 1 1000k
settype decibel out
plot vdb(out) xlimit 1 1000k ylabel 'small signal gain'
settype phase out
plot cph(out) xlimit 1 1000k ylabel 'phase (in rad)'</pre>
<p>
This runs an ac analysis between 1 Hz and 1 MHz with 10 points in every decade,
then plot gain and phase.
<h2> Export and run ngspice </h2>
<p>
Running ngspice the usual way on the export yields the following graph:
<p>
<img src="12_bjt_amp_ac1.png">
<p>
<img src="12_bjt_amp_ac2.png">
<h2> Using other implementations </h2>
<h3> gnucap </h3>
<p>
<b>This may not work with gnucap; error message: <i>open circuit: internal node 2</i> </b>
<p>
Gnucap uses a different command syntax. Modify the spice command symbol's
spice/command attribute to:
<pre>
print ac vdb(out) zp(out)
op
ac dec 10 1 1000k > plot.txt
</pre>
<p>
After the export, write a single word <b>spice</b> in the first line of the
file (e.g. using a text editor), else gnucap won't know the file is in spice
syntax. Then run <i>gnucap 12_btj_amp_ac.cir</i> and it will dump a text
table to plot.txt that can be plotted using e.g. gnuplot. Both traces are
included in the same file.
<p>
The <a href="gnucap/12_btj_amp_ac.rs">gnucap-modified schematics is also available.</a>
<h3> xyce </h3>
<p>
TODO
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