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.

Visual Cues	Narration
Show slide	Welcome to the spoken tutorial on “Operating point analysis in ngspice”
Show slide	In this tutorial we will learn,
Show slide	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.
Show slide	Ubuntu 12.04 is the operating system used with ngspice version 23 installed.
Show slide	Basic knowledge of electronic circuits is a prerequisite for this tutorial. Basic knowledge of Ubuntu Linux and shell commands is also required.
Show slide (hover mouse over circuit diagram) (show nodes a,b,c)	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.
Go to gedit window which is already open hover mouse over components and node information hover over .op Open the terminal window as mentioned Go to the folder containing example1.cir as mentioned Type the commands as mentioned	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 home. 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.
	We will verify Kirchoff's voltage law using the above simulation results.
Slide 5 show circuit hover mouse over the circuit	According to Kirchoff's voltage law, voltage around outer loop should be equal to the value of the dc voltage source V1
Switch to Terminal Type print v(a,b)+v(b,c)+v(c) and Press Enter Key Type print v(a) and press enter	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.
Hover mouse over both the results	Since both voltage values are equal, the Kirchhoff's Voltage law is verified for the outer loop a-b-c-0.
	Now we will simulate this circuit, and verify Kirchoff's voltage law using the command-script included in netlist file.
Show example-modified.cir file already opened	Modified netlist file example-modified.cir is as shown
Show example-modified.cir file	As you can see all the commands we executed in command-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.
Go to the terminal window. On the terminal type source example-modified.cir and press Enter	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
Show slide	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 interactive mode command-line interface & using commandscript included in netlist.
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Show slide	Spoken Tutorial Project is a part of the Talk to a Teacher project It is supported by the National Mission on Education through ICT, MHRD, Government of India More information on this Mission is available at spoken hyphen tutorial dot org slash NMEICT hyphen Intro
	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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