1. Introduction to LTspice IV
Prepared by: Aisha Abdallah
The symbol:

2. Why called LTspice IV?
LTspice IV stands for Linear Technology simulation program with integrated circuit emphasis version 4.
It is freeware software implementing a SPICE simulator of electronic circuits, produced by semiconductor manufacturer: Linear Technology Corporation (LTC)[A.1].
It provides a schematic capture and waveform viewer with enhancements and models to speed the simulation[A.2].
[A.1]
[A.2]

3. Why using LTspice IV?
LTspice IV can do simulation for advanced technologies; e.g. 90nm, 65nm, … etc, while PSpice A/D cadence version 16.0 can not withstand for new technology process.

4. Start your LTspice IV file
After downloading LTspice IV from

5. The following website appears. Choose Download LTspice IV for Windows

6. Start your LTspice IV file
double click on LTspice IV icon
To start your work:
File New Schematic

7. Or press on New Schematic

8. This icon appears after selecting New schematic

9. Example
Build voltage divider circuit; which consists of two resistors, their values 1k and 2k, and 10V voltage supply.

10. After you press on component icon, the following window appears
Press on component icon to get the elements
Write in this box or search to get the element

11. To get voltage supply, you can write voltage, battery, or cell
To get voltage supply, you can write voltage, battery, or cell. All of them give you voltage source either DC, AC, Pulse, Sine, PWL, Exp, or SFFT.

12. If it is DC voltage source enter its value here
Right click on the element to choose its type and to specify its value.
If not press Advanced

13. Select the type of signal
AC Value

14. Enter the value of resistor

15. To insert the ground
Another way to insert resistor

16. To connect elements using wire

17. * Simulate the circuit by choosing Simulate  run

18. Select type of analysis

19. After selecting type of analysis and choosing the node, the plot window appears.
The output

20. How to deal with MOSFET?
There are two types of MOS for both NMOS and PMOS in LTspice IV:
nmos and pmos: the substrate is connected to the source.
nmos4 and pmos4: the substrate is not connected to the source. For this type you can add the model you are working on; e.g. TSMC or IBM 0.25μm, 90nm, …, etc.

21. The model of NMOS should be saved in notepad (
The model of NMOS should be saved in notepad (.txt) where here the name of the model is CMOSN

22. How to deal with MOSFET?
nmos
nmos4

23. Choosing nmos4 right click on it the following window appears
Name of the model
Width of transistor
Length of transistor

24. To write the model file
Select SPICE directive
Write
.include name_of_the_txt_model_file.txt
Note: it should be saved in the file that your are working on for LT spice file.

25. After connecting the circuit as shown and selecting the type of analysis which is
.dc VG m
, the circuit is completed.

26. Press plot simulation after selecting plot window, then press Visible Trance

27. When you press on Visible Trance the following window appears
When you press on Visible Trance the following window appears . Then select the variable you want .

28. To copy the plot go to Tools Copy bitmap to clipboard, then paste it in your document.

29. To export the plot to Matlab
go to
FileExport

30. This window will appear. Select the variable that you want
This window will appear. Select the variable that you want. By default it also exports the x-axis variable; in this plot is Vg. The exported file will be saved in the current file you are working in as notepad file .txt

31. The exported file contains two columns, Vg and Id(M1)

32. This is the m.file that must be saved in the current file you are working in.
% post process an LT-spice simulation with Matlab clear all; clc; close all; % dlmread: read ASCII-delimited file of numeric data into matrix data = dlmread('model1_IdvsVgs90.txt','',1,0) %(‘name of txt file’, skip one row (headings)) % '' means let Matlab figure out the delimiter % 1,0 means read data whose upper left corner is at row 1 and col 0 VGS = data(:,1); ID = 1000*data(:,2); % to make current in mA %plot the magnitude frequency response of the RC circuit plot(VGS,ID) xlabel('V_G_S(V)'); ylabel('I_D(mA)'); title(' The IV Characteristic of NMOS transistor using 90nm technology') grid
The Matlab code is from:

33. Matlab plot

34. Extra about LTspice plot
How to thicken up the lines in your schematic or simulations?
1. Open the control panel (tools menu bar). 2. To thicken the schematic lines, Select the Drafting Options tab and check "Draft Thick Lines“. 3. To thicken simulation lines, Select the Waveforms tab and check "Plot data with thick lines“.

35. Extra about LTspice
Can LTspice deal with netlist? Yes, the user can start working on LTspice using netlist. Fileopenselect Netlist .cir  type any name of non-exist file then the netlist window will be open.

36. Extra references http://denethor.wlu.ca/ltspice/

37. To plot the power dissipation http://www.linear.com/solutions/1148
To plot the power dissipation
A very good book to start and deal with LTspice
E. Bruun, CMOS Integrated Circuit Simulation with LTspice IV a Tutorial Guide, 1st ed., 2015.
Erik Bruun’s book is available on:

38. Thank you