LTspice IV Application Handbook - Preface & extracts

sleuz — Wed, 15 Jan 2014 08:06:37 GMT

Current Revision posted to Documents by sleuz on 1/15/2014 8:06:37 AM

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).

community.element14.com/.../4784.contentimage_5F00_29304.html

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.

community.element14.com/.../4784.contentimage_5F00_29304.html open file	community.element14.com/.../4784.contentimage_5F00_29304.html pick visible traces
community.element14.com/.../4784.contentimage_5F00_29304.html save file	community.element14.com/.../4784.contentimage_5F00_29304.html autorange
community.element14.com/.../4784.contentimage_5F00_29304.html control panel	community.element14.com/.../4784.contentimage_5F00_29304.html tile windows
community.element14.com/.../4784.contentimage_5F00_29304.html run simulation	community.element14.com/.../4784.contentimage_5F00_29304.html cascade windows
community.element14.com/.../4784.contentimage_5F00_29304.html pause simulation	community.element14.com/.../4784.contentimage_5F00_29304.html close all
community.element14.com/.../4784.contentimage_5F00_29304.html zoom in	community.element14.com/.../4784.contentimage_5F00_29304.html cut
community.element14.com/.../4784.contentimage_5F00_29304.html pan	community.element14.com/.../4784.contentimage_5F00_29304.html search
community.element14.com/.../4784.contentimage_5F00_29304.html zoom out	community.element14.com/.../4784.contentimage_5F00_29304.html print setup
community.element14.com/.../4784.contentimage_5F00_29304.html zoom full extents	community.element14.com/.../4784.contentimage_5F00_29304.html print

Figure 3.4

community.element14.com/.../4784.contentimage_5F00_29304.html create new schematic	community.element14.com/.../4784.contentimage_5F00_29304.html place a capacitor
community.element14.com/.../4784.contentimage_5F00_29304.html zoom in	community.element14.com/.../4784.contentimage_5F00_29304.html place an inductor
community.element14.com/.../4784.contentimage_5F00_29304.html pan	community.element14.com/.../4784.contentimage_5F00_29304.html place a diode
community.element14.com/.../4784.contentimage_5F00_29304.html zoom out	community.element14.com/.../4784.contentimage_5F00_29304.html place a component
community.element14.com/.../4784.contentimage_5F00_29304.html zoom full extent	community.element14.com/.../4784.contentimage_5F00_29304.html move an element
community.element14.com/.../4784.contentimage_5F00_29304.html cut	community.element14.com/.../4784.contentimage_5F00_29304.html move an element and its connections
community.element14.com/.../4784.contentimage_5F00_29304.html copy	community.element14.com/.../4784.contentimage_5F00_29304.html undo
community.element14.com/.../4784.contentimage_5F00_29304.html paste	community.element14.com/.../4784.contentimage_5F00_29304.html redo
community.element14.com/.../4784.contentimage_5F00_29304.html wire components	community.element14.com/.../4784.contentimage_5F00_29304.html rotate an element
community.element14.com/.../4784.contentimage_5F00_29304.html ground	community.element14.com/.../4784.contentimage_5F00_29304.html mirror an element
community.element14.com/.../4784.contentimage_5F00_29304.html place and edit a label	community.element14.com/.../4784.contentimage_5F00_29304.html place and edit new text on the schematic
community.element14.com/.../4784.contentimage_5F00_29304.html place a resistor	community.element14.com/.../4784.contentimage_5F00_29304.html place and edit a SPICE directive on the schematic

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 community.element14.com/.../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).

community.element14.com/.../4784.contentimage_5F00_29304.html

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.

community.element14.com/.../4784.contentimage_5F00_29304.html

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.

community.element14.com/.../4784.contentimage_5F00_29304.html

Figure 3.8

5. We are now going to add two transistors to our schematic. Once again, click on the AND icon community.element14.com/.../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.

community.element14.com/.../4784.contentimage_5F00_29304.html

Figure 3.9

6. If you’re not happy with the location of a component, you can remove it with community.element14.com/.../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 community.element14.com/.../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"

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