View source for Ngspice/C2/Operating-point-analysis-in-NGspice/English

'''Title of the Script:''' Operating point analysis using ngspice

'''Author:''' Abhishek, IIT Bombay

'''Keywords: '''video tutorial,''' '''ngspice. 


{| style="border-spacing:0;"
| style="border-top:0.1pt solid #000000;border-bottom:0.1pt solid #000000;border-left:0.1pt solid #000000;border-right:none;padding:0cm;"| <center>'''Visual Cues'''</center>
| style="border:0.1pt solid #000000;padding:0cm;"| <center>'''Narration'''</center>

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| style="border-top:none;border-bottom:0.1pt solid #000000;border-left:0.1pt solid #000000;border-right:none;padding:0cm;"| <center>Show slide</center>
| style="border-top:none;border-bottom:0.1pt solid #000000;border-left:0.1pt solid #000000;border-right:0.1pt solid #000000;padding:0cm;"| Welcome to the spoken tutorial on “'''Operating point analysis in ngspice'''”

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| style="border-top:none;border-bottom:0.1pt solid #000000;border-left:0.1pt solid #000000;border-right:none;padding:0cm;"| <center>Show slide</center>
| style="border-top:none;border-bottom:0.1pt solid #000000;border-left:0.1pt solid #000000;border-right:0.1pt solid #000000;padding:0cm;"| In this tutorial we will learn, 

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| style="border-top:none;border-bottom:0.1pt solid #000000;border-left:0.1pt solid #000000;border-right:none;padding:0cm;"| <center>Show slide</center>
| style="border-top:none;border-bottom:0.1pt solid #000000;border-left:0.1pt solid #000000;border-right:0.1pt solid #000000;padding:0cm;"| To perform '''operating''' '''point''' '''analysis.'''

To verify '''Kirchoff's''' '''voltage''' '''law''' using '''ngspice''' in,


'''interactive mode '''using''' command-line interface &'''

'''commandscript included in netlist file.'''

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| style="border-top:none;border-bottom:0.1pt solid #000000;border-left:0.1pt solid #000000;border-right:none;padding:0cm;"| <center>Show slide</center>
| style="border-top:none;border-bottom:0.1pt solid #000000;border-left:0.1pt solid #000000;border-right:0.1pt solid #000000;padding:0cm;"| '''Ubuntu''' 12.04 is the '''operating''' '''system''' 


used with '''ngspice''' '''version''' 23 '''installed.'''

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| style="border-top:none;border-bottom:0.1pt solid #000000;border-left:0.1pt solid #000000;border-right:none;padding:0cm;"| <center>Show slide</center>
| style="border-top:none;border-bottom:0.1pt solid #000000;border-left:0.1pt solid #000000;border-right:0.1pt solid #000000;padding:0cm;"| Basic knowledge of '''electronic''' '''circuits''' is a prerequisite for this tutorial.


Basic knowledge of '''Ubuntu''' '''Linux''' and '''shell''' '''commands''' is also required.

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| style="border-top:none;border-bottom:0.1pt solid #000000;border-left:0.1pt solid #000000;border-right:none;padding:0cm;"| <center>Show slide</center>

<center>(hover '''mouse''' over '''circuit''' '''diagram''')</center>

<center>(show '''nodes''' a,b,c)</center>
| style="border-top:none;border-bottom:0.1pt solid #000000;border-left:0.1pt solid #000000;border-right:0.1pt solid #000000;padding:0cm;"| We will use the example '''circuit''' shown.


The '''circuit''' consists of three prominent '''nodes''' “a”, “b” and “c”. 


In addition, a fourth '''node''' called as '''reference''' OR '''datum''' '''node''' must be marked as '''node''' “0”. This is mandatory for any '''circuit.''' 




|-
| style="border-top:none;border-bottom:0.1pt solid #000000;border-left:0.1pt solid #000000;border-right:none;padding:0cm;"| <center>Go to '''gedit''' '''window''' which is already open</center>


<center>hover '''mouse''' over '''components''' and '''node''' information</center>


<center>hover over '''.op'''</center>


<center>Open the '''terminal''' '''window'''</center>

<center>as mentioned</center>


<center>Go to the '''folder''' containing </center>

<center>'''example1.cir''' as mentioned</center>


<center>Type the '''commands''' as mentioned</center>
| style="border-top:none;border-bottom:0.1pt solid #000000;border-left:0.1pt solid #000000;border-right:0.1pt solid #000000;padding:0cm;"| Let us open the '''ngspice''' '''netlist''' '''example1.cir''' '''file''' corresponding to the '''circuit''' '''schematic''' shown before, in a '''text''' '''editor.'''


I have already opened this in '''gedit''' '''text''' '''editor.'''


Note that the '''netlist''' '''file''' is saved with '''.cir''' '''extension''' 


We can see all the '''components''' like '''voltage source, resistors and current source'''


also information about '''nodes''' connecting them together.


.'''op command''' included in '''netlist''' '''file''' is used to perform '''operating point analysis'''


Now we will '''simulate''' this '''circuit,''' and verify '''Kirchoff's''' '''voltage''' '''law''' using the '''interactive mode-command-line interface.'''


let us open '''ngspice''' through '''terminal.''' 


Go to top left corner of '''Ubuntu''' '''desktop''' '''screen.'''


Click on '''Dash hom'''e.


In the '''search''' '''bar,''' '''write''' '''terminal''' and press '''Enter.'''


This will open '''Terminal''' '''window.'''


Let me resize this window


Now I go to the '''folder''' where the '''netlist''' '''file''' '''example1.cir''' is '''saved.'''

I do this as follows:


On '''terminal,''' I will type '''cd Desktop/op-analysis '''and press '''Enter.'''


Now let us '''simulate''' the '''ngspice''' '''file.''' 


Let us see how this can be done.


On '''terminal,'''


Type '''ngspice space example1.cir''' and press '''Enter.'''


Here you will notice that we have entered into the '''ngspice''' '''command''' '''line interface'''.


Type '''run '''and''' '''press '''Enter''' 


This will '''simulate''' the '''circuit''' and '''store''' the results.

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| style="border-top:none;border-bottom:0.1pt solid #000000;border-left:0.1pt solid #000000;border-right:none;padding:0cm;"| 
| style="border-top:none;border-bottom:0.1pt solid #000000;border-left:0.1pt solid #000000;border-right:0.1pt solid #000000;padding:0cm;"| We will verify '''Kirchoff's voltage law '''using the above '''simulation''' results.

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| style="border-top:none;border-bottom:0.1pt solid #000000;border-left:0.1pt solid #000000;border-right:none;padding:0cm;"| Slide 5

show '''circuit'''

hover '''mouse''' over the '''circuit'''
| style="border-top:none;border-bottom:0.1pt solid #000000;border-left:0.1pt solid #000000;border-right:0.1pt solid #000000;padding:0cm;"| According to '''Kirchoff's voltage law,'''


'''voltage''' around outer loop should be equal to the value of the '''dc''' '''voltage''' '''source''' V1




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| style="border-top:none;border-bottom:0.1pt solid #000000;border-left:0.1pt solid #000000;border-right:none;padding:0cm;"| Switch to '''Terminal'''


Type '''print v(a,b)+v(b,c)+v(c)''' and Press '''Enter''' Key


Type '''print v(a)''' and press '''enter'''



| style="border-top:none;border-bottom:0.1pt solid #000000;border-left:0.1pt solid #000000;border-right:0.1pt solid #000000;padding:0cm;"| Calculate '''voltage''' around the outer '''loop.''' For this, let us do the following:


On to the '''Terminal''' ,


Type “'''print space v(a,b)+v(b,c)+v(c)''' and press '''Enter''' Key


Here '''v(a,b)''' denotes the''' voltage drop''' between the '''nodes''' a and b and so on.


'''print command''' '''displays''' the results of the calculation mentioned to its right side.


Notice the result of the '''calculation''' in the '''terminal.'''


It is 30 '''volt''' as shown


Now '''calculate''' the value of '''DC''' '''voltage''' '''source''' V1 that is v(a).


Type '''print space v(a)''' and press '''Enter'''

Notice the result of the '''calculation''' in the '''terminal.'''


If both the results are equal then '''Kirchoff's voltage law''' is verified.




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| style="border-top:none;border-bottom:0.1pt solid #000000;border-left:0.1pt solid #000000;border-right:none;padding:0cm;"| Hover '''mouse''' over both the results
| style="border-top:none;border-bottom:0.1pt solid #000000;border-left:0.1pt solid #000000;border-right:0.1pt solid #000000;padding:0cm;"| Since both '''voltage''' values are equal, the '''Kirchhoff's Voltage law''' is verified for the outer loop '''a-b-c-0.'''




|-
| style="border-top:none;border-bottom:0.1pt solid #000000;border-left:0.1pt solid #000000;border-right:none;padding:0cm;"| 
| style="border-top:none;border-bottom:0.1pt solid #000000;border-left:0.1pt solid #000000;border-right:0.1pt solid #000000;padding:0cm;"| Now we will '''simulate''' this '''circuit,''' and verify '''Kirchoff's voltage law''' using the '''command'''-script included in n'''etlist file'''.

|-
| style="border-top:none;border-bottom:0.1pt solid #000000;border-left:0.1pt solid #000000;border-right:none;padding:0cm;"| <center>Show '''example-modified.cir''' '''file''' already opened</center>
| style="border-top:none;border-bottom:0.1pt solid #000000;border-left:0.1pt solid #000000;border-right:0.1pt solid #000000;padding:0cm;"| Modified '''netlist''' '''file''' '''example-modified.cir''' is as shown




|-
| style="border-top:none;border-bottom:0.1pt solid #000000;border-left:0.1pt solid #000000;border-right:none;padding:0cm;"| <center>Show '''example-modified.cir''' file</center>
| style="border-top:none;border-bottom:0.1pt solid #000000;border-left:0.1pt solid #000000;border-right:0.1pt solid #000000;padding:0cm;"| As you can see all the '''commands''' we executed in c'''ommand-line interface''' are included in this '''netlist''' as '''control''' '''statements.'''


That is the statements in between the''' .control '''and the '''.endc''' statements.


'''Echo''' command will '''echo''' the text written to its right side, on the '''terminal''' '''window.'''


You can see that we have included the '''print''' statements in the '''netlist.'''

|-
| style="border-top:none;border-bottom:0.1pt solid #000000;border-left:0.1pt solid #000000;border-right:none;padding:0cm;"| <center>Go to the '''terminal''' '''window.'''</center>


<center>On the '''terminal''' type '''source example-modified.cir '''and press '''Enter'''</center>
| style="border-top:none;border-bottom:0.1pt solid #000000;border-left:0.1pt solid #000000;border-right:0.1pt solid #000000;padding:0cm;"| Now we execute the modified '''netlist''' '''file.'''


'''source''' command is used to '''simulate''' the '''netlist''' from within the '''ngspice simulator environment'''


On the '''terminal''' type '''source space example-modified.cir''' and press '''Enter.'''


This will run the '''simulation''' and directly show the results for '''KVL''' verification. 


You can see that results are the same as seen earlier.


This brings us to the end of this tutorial.


Quit the '''ngspice simulator''' by typing '''quit '''and press '''Enter. key'''

|-
| style="border-top:none;border-bottom:0.1pt solid #000000;border-left:0.1pt solid #000000;border-right:none;padding:0cm;"| <center>Show slide</center>
| style="border-top:none;border-bottom:0.1pt solid #000000;border-left:0.1pt solid #000000;border-right:0.1pt solid #000000;padding:0cm;"| Now let us summarize what we learnt in this tutorial.

In this tutorial we learnt,

To perform '''operating point analysis''' of a given '''circuit.'''

To verify '''Kirchhoff's voltage law''' using '''ngspice''' through i'''nteractive mode '''

'''command-line interface &'''

using''' commandscript included in netlist.'''

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| style="border-top:none;border-bottom:0.1pt solid #000000;border-left:0.1pt solid #000000;border-right:none;padding:0cm;"| <center>Show slide</center>



| style="border-top:none;border-bottom:0.1pt solid #000000;border-left:0.1pt solid #000000;border-right:0.1pt solid #000000;padding:0cm;"| Watch the video available at the following link 

* It summarises the Spoken Tutorial project 

* If you do not have good bandwidth, you can download and watch it 



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| style="border-top:none;border-bottom:0.1pt solid #000000;border-left:0.1pt solid #000000;border-right:none;padding:0cm;"| <center>Show slide </center>
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| style="border-top:none;border-bottom:0.1pt solid #000000;border-left:0.1pt solid #000000;border-right:none;padding:0cm;"| <center>Show slide</center>
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| style="border-top:none;border-bottom:0.1pt solid #000000;border-left:0.1pt solid #000000;border-right:none;padding:0cm;"| 
| style="border-top:none;border-bottom:0.1pt solid #000000;border-left:0.1pt solid #000000;border-right:0.1pt solid #000000;padding:0cm;"| Thank you for joining. 

Hope you found this tutorial useful. 

This is Rupak Rokade from IIT Bombay signing off. 


Thank You.

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