LTSPICE IV: EXTRACT
1.1 Circuit simulation with LTspice IV
1.1.1 Three basic steps
With LTspice IV, circuit simulation is easy as 1, 2, 3 (see fig.1.1):
• First step: Create the schematic and choose the type of simulation. With the schematics editor, you can
draw your circuit and add your comments. LTspice IV offers a wide range of components, however, if one or more
models of components are missing, you can download them online. (See chapter 12 for more information about
this).
Depending on your requirements (continuous, alternative or transient analysis), choose a simulation directive and
add the relevant source (see chapters 9 to 11 and 13). You can also add other commands (simulation directives)
and configure all the elements, components values, etc.
• Second step: Run the simulation. You are asking the computer to carry out all calculations required to perform
the chosen simulation, this is called running the simulation. This step takes a little time for all calculations to be
done.
• Third step: Take the measurements. You choose the measures you require (current, voltage, frequency, power,
etc.). The measurements are displayed instantly in a screen looking like the display of a high-performance digital
oscilloscope. You can configure the display parameters in the same manner as you would on a real oscilloscope
(reframing, change of scale, zoom, colour choice, screen fractioning, traces multiplication).
Figure 1.1
2. You create a new page for your schematic by clicking on the red icon on white background in the top left corner. You will see the background turn a lighter shade of grey and all 37 icons are now active. The number of menus increases as well and their content is now relevant to the schematics editor you have just accessed.
LTspice IV is now waiting for you to either draw or open a schematic. The complete description of the new menus of the schematic editor can be found in chapter 4.
Figure 3.4
Figure 3.5
3.4.1 Drawing a schematic
3. We are not going to open a saved schematic, but we are going to create our own in order to go through all the creation steps. To start with, let’s position on our schematic an operational amplifier symbol. To do so, click on
the icon representing the AND logic gate symbol https://community.element14.com/resized-image/__size/1200x900/__key/communityserver-wikis-components-files/00-00-00-00-56/4784.contentimage_5F00_29304.html. Click once on this icon and another window appears. The 
left-hand column contains a series of words in brackets. In this column, double-click on [Opamps] to access the
operational amplifier directory. (See figure 3.6).
Figure 3.6
A list of operational amplifier appears, scroll to the very end of this list and double-click on UniversalOpamp2, which is currently the last item in the list. It is a standard operational amplifier with average performances. (Figure
3.7).
4. You automatically come back to the schematic page and your cursor is now shaped like an operational amplifier symbol. Go to the centre of the page and click left to drop the symbol on the schematic, figure 3.8. Another copy of this symbol appears straight away and follows the movement of your mouse.
Figure 3.7
To get rid of it (we only want to use one operational amplifier on this schematic), right click anywhere, and the symbol disappears. So at the moment, the only item on our schematic is the operational amplifier in the centre.
Figure 3.8
5. We are now going to add two transistors to our schematic. Once again, click on the AND icon https://community.element14.com/resized-image/__size/1200x900/__key/communityserver-wikis-components-files/00-00-00-00-56/4784.contentimage_5F00_29304.html, you can see 
that you are still in the operational amplifiers directory.
So click on the yellow folder icon on the left to go back up one level in the directory. We are now in the standard component directory, in the 4th column, you’ll see the word npn, double-click on it, see figure 3.9.
As before, you find yourself straight back in the schematic page where you can place your NPN bipolar transistor by following the same procedure as for the amplifier: Click to drop, then, right-click to remove the copy.
Figure 3.9
6. If you’re not happy with the location of a component, you can remove it with https://community.element14.com/resized-image/__size/1200x900/__key/communityserver-wikis-components-files/00-00-00-00-56/4784.contentimage_5F00_29304.html. Click on the scissors, then click 
on the component you wish to remove, and lastly, right-click to exit the cut function. You can also use the open hand to move a component. Click on the hand, then click on the component, it changes colour, move your 
mouse to place it where you want and click again to drop it, then right-click to exit the move function. You can also click and drag your mouse to draw a box around the section to move, then, move the box, click to drop it and right-click to exit.
7. We are now going to add another PNP bipolar transistor. Click on AND https://community.element14.com/resized-image/__size/1200x900/__key/communityserver-wikis-components-files/00-00-00-00-56/4784.contentimage_5F00_29304.html, and double-click on the word pnp, 
figure 3.10. Position the symbol as you see it on the schematic, but do not click to drop it, at this stage, you only have the outline of the symbol. Then to flip the symbol, you must use twice the rotation tool (command Ctrl + R) or then 
once the symmetry tool (command Ctrl + E) or , figure 3.11. Once the symbol has the required orientation, 
click to drop it.
Interested? Order the Application Handbook "The LTspice IV Simulator"