In order to begin to learn the use Micro-Cap,  it will be instructive to create and analyze a simple Op-Amp circuit. The first step is to draw the circuit on the computer by selecting components and connecting them together. Follow the step by step procedure.

First start the Micro-Cap program by clicking on the Micro-Cap Icon on the desktop or in the Windows Start, Programs, Micro-Cap window. This will bring up the following program window:

Figure 1

The menu at the left of the screen in the picture above contains a list of component categories.  The Analog Primitives group has been opened showing sub categories below it.  The connectors category in this group has been opened. The ground element has been selected and a ground element has peen placed in the drawing window.  For Circuits I students this category, the passive components category, and the waveform sources category will be of interest.  The ground from the connector category must be used at least once in every circuit to identify the reference node.  The resistor, capacitor, and inductor from the passive components category will be used.  The battery and various voltage and current sources may be used. Electronics students will also use the active devices category and some additional passive devices.  The components may also be selected from the dropdown menus accessed at the top of the screen as shown below.

Figure 2

The more commonly used components can also be selected by clicking on the icons below the menu line.

Figure 3

Just below Analysis in the top menu line you will find the ground symbol, followed by the resistor, Capacitor, inductor, diode, bipolar transistor, field effect transistor, op-amp, digital clock stimulus generator, battery, current source, and voltage source.  The last two sources are pulse generating sources, so beginning students will need to look under waveform sources for the types of source they are likely to use.

Below the component icons is a row of various functions that can be performed while setting up a circuit.  The arrow at the left end is the select tool.  It is used to select parts of a circuit in order to modify, move, or delete them.  The highlighted icon next to the select tool is the component placement tool.  It is highlighted to indicate that it is the currently selected or active tool.  Next is the test tool, used to label the circuit and add comments to the circuit diagram. The text tool is followed by the right angle wiring tool.  This tool allows components to be connected together with horizontal and vertical lines only.  Components can be connected using diagonal lines using the fifth icon.  some of the other tools will be explained later.  You can find out what other icons do by hovering the cursor over the icon until a box with the name of the tool appears.  Then go to help in the top menu line and look up that name.

Simple DC circuit

For beginning Electric Circuits students we will build and analyze a simple DC circuit.  Electronics students may wish to also try this or may jump the the Op-Amp and transistor circuits that follow.

We will start with a simple resistor and battery circuit.  Start by selecting the resistor component by clicking on the resistor icon or from the passive components list under Analog Primitives.  The cursor will change to a resistor symbol.  If the resistor has the desired orientation, that is horizontal or vertical, then just move it to the place where you want it and click the left mouse button.  If it does not have the correct orientation then hold down the left mouse button while clicking the right button.  This will cause the resistor or any other component to rotate 90^o.  Then still holding the left button down move it to the desired position and release.  At this time The resistor model box will appear with the resistor value entry highlighted.  The cursor will already be in the value window.  Just type in the desired value.  Micro-Cap recognizes most unit prefixes, but it does not distinguish between upper and lower case.  Therefore m or M will both represent milli.  To get a meg prefix you must type meg or MEG or mEg any combination of upper and lower case letters will be the same to Micro-Cap.  To get micro type u.  this is used because the lower case u looks somewhat like the Greek lowercase mu used as the symbol for micro.

Figure 4

Below the value for 1.5 kW has been entered in the value window.  Note that the Show box is checked by default, so that the value will be shown on the diagram along with the part number R1. 

Figure 5

Place the three resistors as shown below. 

Figure 6

The batteries can then be added by clicking on the battery icon at the top of the screen or by clicking on battery under the waveform sources category of Analog Primitives.  The battery properties box will come up with VALUE selected.  Type in 15 for the battery on the left, V1, and 20 for the one on the left.  Note that the part number V1 appears for the first battery above but not its value that is because I unchecked the Show box next to the value for that source.  Only the voltage value shows for the second source since I left the value Show box checked and then I selected the part=V2 from the property list and unchecked the Show check box for the part number as shown below.

Figure 7

The next task is to connect all the components together.  Click on the Wire Mode icon, the one just after the bold face capital T shown in Figure 3, or just press (ctrl-w).  Note: many of the Micro-Cap tools have shortcuts involving combinations of the ctrl key or alt key and another key to activate them.  If you hover the mouse over the tool icon a small box showing the Text Mode shortcut will appear.  After selecting the wire mode tool, start at the end of a component that you want to wire to another component.  Then move the cursor up and over, or over and up as the case may be.  The wire mode tool remembers which way you first start moving the cursor after you click to start a wire.  After that if you want to move horizontally and then down but moved down a little first your final wire wil go down first and then over as in the highlighted line in Figure 8 below.  Don't worry.  As long as the last item you placed is still highlighted you can delete it by pressing the delete key.  You might want to just try out the wire mode tool on any empty spot and try moving the cursor around to see what happens when you try to change the direction of the initial part of the wire.  Then delete it when you are done  Note that in the figure below I connectedV1 to R1 and the other end of R1 to the top of R3.  Then I started at the right end of R2 and connected it to the 20 volt battery.  Since I started down first the only way Micro-Cap would let me finish the connection was down and then over.  Since this looks a little strange I deleted it and started over making sure to move the cursor horizontally first then down.

Figure 8

I followed that by making the other connections.  Note that at the middle node on both the top and bottom of the circuit there is a dot at the junction of the wires.  This is done automatically by Micro-Cap when you bring the end of one wire in contact with the middle of another.  If you draw one wire across another without ending on the other there will be no dot and more important there will be no connection between those wires in the circuit, just like the normal convention for drawing circuits.

Figure 9

Figure 10

If you want to change the value of a component you can change to the select tool, the black arrow on the left edge of Figure 3, and then double click on the component to bring up the property box for that component.  That works for any component, but for components that have a single value and have that value displayed on the circuit diagram, you can just double click on the value and edit the value in the box as shown for R3 in Figure 10 above.  When you press enter or click somewhere else on the circuit window the edit box will disappear and the new value will be displayed where the original value was.  If you don't like the placement of the values or the part numbers you can use the select tool click and drag them somewhere else.

Analyzing the circuit:

The easiest way to analyze the circuit to determine the DC node voltages and branch currents is to use Transient Analysis.  Later you can learn how to use DC Analysis to show the change in a circuit value as the value of one of the DC sources changes.  Click on Analysis in the top menu bar.  Then click on Transient from the dropdown menu list, or you could just press (Alt-1).  Note the other shortcuts in the dropdown list shown in Figure 11.

Figure 11

The Transient Analysis window with the Transient Analysis Limits box showing.  Since you will not be actually performing a transient analysis, you do not have to worry about any of the limits. 

Simple Op-Amp circuit

For electronics students we will create and analyze a simple Op-Amp circuit.  To select the components to build your circuit, first select Component from the menu at the top of the window. Then select Analog Primitives from the drop down menu that appears. From the second drop down menu select the type of device you want. Finally select the desired component to be added to your circuit from the last pull down menu that appears. You may now insert as many of that component into the circuit as you need. Each copy may have its own unique value. Just press and hold the left mouse button and move the mouse cursor to the desired position for the component. While still holding the left mouse button down the component may be rotated by clicking the right mouse button, 90^o for each click. Release the mouse button when the component position and orientation are as desired. At this point a component properties menu will appear and you can enter a value or other part identification. You can add more of these components by again clicking the left mouse button and placing the component.

Next select Waveform sources from the Analog Primitives menu, then select Sine Source from the Waveform Sources menu.  Note the ten most recently used components also appear in a numbered list at the bottom of the components drop down menu.

Some of the most frequently used components are available directly on the toolbar of the newer versions of the Micro-Cap.  This saves time since you do not have to go through the series of menus to access these commonly used components. Note:  The ground, Resistor, Capacitor, Diode, NPN Transistor, Digital Logic Inverter, Battery, Pulse source, and Sine source are shown in the top row of the toolbar above.  Just click on the one you want and start placing the component in your circuit.

With later versions some additional component icons are included.  The component Icons start with the ground icon just below the "A" in the word Analysis in the menu bar and then continue with: resistor, capacitor, inductor, diode, NPN transistor, NMOS transistor, Op-Amp, Digital Logic Inverter, battery, Pulse voltage source, and Sine voltage Source.  Note: You can find out what each Icon does by placing the mouse cursor over the icon.  In a short time a small box appears with a short name or description.  At the same time a longer description appears in the space at the bottom edge of the Micro Cap window.  Below is a shot of the display when the mouse cursor is on the diode symbol.

Place the source about half way down at the right edge of the screen, by moving the cursor to the desired position then click and hold the left mouse button. If the + sign is not at the top of the symbol then click the right mouse button until it is.  Then if the position looks good release the left mouse button.

After releasing the mouse button a component Model window will appear at the top of the screen.

Type in the name to be used for the sine source (Vs).  Then click in the small square box labeled Display which is next to the value box.  This will cause the value, "Vs", to be displayed in the diagram next to the component.  Next click on the PART=V1 line in the big rectangle below.  This will put the part number in the value window.  Click the display box next to it to turn display off.  Then press enter or click on the OK button.

The sine source now appears with its Name
 

In version 2.1 or later you can click on the text tab at the bottom of the window to switch to the model text screen and then click on the Page 1 tab to switch back. In older versions press Ctrl+g (hold down the control key and press g) and the active window will switch between the circuit window and the model window.

The model statement for the sine source should be showing.

You can now edit the model as desired by adding or changing the text in the model statement.  The blank space between the ( ) means that the default settings have been used.  The picture below shows what these settings are.

You should change the frequency from F=1MEG(1 MHz = 10⁶ Hz) to F=1k or F=1000 for 1 kHz frequency and the amplitude from A=1 to A=.5 for a 0.5 volt signal amplitude.  The other parameters in the model statement for the sine source are as follows:
DC = the dc offset voltage (default = 0).
PH = the phase angle of the source (default = 0).
RS = the internal resistance of the source (default = 1 milli-Ohm).
RP = repetition period of exponential amplitude modulation. See complete description in the HELP file under sine source. (default=0)
TAU = the time constant for the exponential. (default=0)

After making the changes go back to the circuit page by clicking on the page 1 tab at the bottom of the page or by pressing (CTRL-G).
 

Next Select Resistor from the Passive Components sub menu of the Analog Primitives menu or by clicking on the resistor icon at the top of the screen.

Place a resistor running vertically near the middle of the right edge of the screen and give it a value of 1k. Note: there should be no blank spaces between the number and the suffix for the value.
 
 Note the position of the cursor arrow in the illustration above. This icon is used to toggle node numbers on and off each time you click on it. Try it. The node numbers that appear on the screen are assigned by the program in the order that the components are placed in the drawing. Nodes 1 and 2 appear on the first component and nodes 3 and 4 appear on the second component. Later when the current nodes 2 and 3 are connected to ground which is by definition node 0, the node number that is currently 4 will become node 2. This will simplify keeping track of the nodes we need to refer to in the analysis operations later, since the input will be node 1 and the output will be node 2.

Next add an Op-Amp to the circuit by selecting Op-Amp from the Active Devices menu or the Op-Amp icon at the top of the screen. Position the Op-Amp near the middle of the screen as shown below.  You may have to rotate it to get the inverting input (node 6 in the picture below) at the top.

Select LM741 as the model name. Move down the list of available Op-Amp types until you find the LM741A and click on it. This  will insert that name in the value window and also insert the proper data into the .MODEL statement in the text window for use by the analysis portion of the program.  Then click on the display box to the right of the value window to have this value displayed on the circuit diagram.  If you click on the PART= line then the part number will appear in the value window and you can turn off the display of the part number and have only the model name displayed as shown above.

Note that the Op-Amp symbol has been rotated so that the + or non-inverting input is at the bottom.  If you did not get it placed this way you can change it by using the select tool.  This is the arrow icon shown at the left end of the second row if icons in the picture below.  Click on this icon and then use it to select the Op Amp by pressing and holding the left mouse button and then rotate the symbol with the right mouse button until you get the desired orientation.

Press Ctrl+g or click on the text tab to look at the model window. The LEVEL parameter indicates the type of mathematical model that will be used to simulate the Op-Amp. Level 1 is an ideal Op-Amp, level 2 includes the non ideal frequency response characteristics and level 3 includes all the limitations of real Op-Amps. We will normally use level 3. The other parameters indicate the ac and dc output resistance, the input offset voltage and currents, the positive and negative slew rates, input bias currents, and a number of other parameters. There are several parameters not shown which are set to default values. The values that appear in this model statement show where the specific model for the LM741A is different from the Micro Cap default Op-Amp Model. Pressing Ctrl+g again or clicking on the page 1 tab takes you back to the circuit window.

Now add two more resistors and a capacitor as shown.  Note that using a lower case u and an Upper case F on the capacitor value gives the appearance of the normal micro Farad units (µF).
 
 

Now it is time to connect the components together. Note the fourth icon in the second row in the illustration of the Op-Amp model statement above. This icon is the connector tool for making connections that have only right angle corners. Click on this icon and then move the cursor to one of two nodes that you want connected together. Then press and hold the left mouse button and move to the other node and release the button. There are two possible right angle paths between most nodes. The one that will be used is determined by the first movement of the mouse after pressing the button. If you press the mouse button and move the mouse vertically first and then horizontally the path will leave the first node vertically and enter the second node horizontally. This will be reversed if your first movement after pressing the mouse button is horizontal.  Next to this icon is a tool for making diagonal connections at any angle.  Usually the circuit diagram will look better with all horizontal and vertical lines.

Note that one of the node numbers from the resistor R2 has disappeared. This is because it is now a part of the top node of the sine source. If one of the two node numbers does not disappear then you have not started the connection exactly on one of the nodes. Connections to components can only be made at the very end of the terminal. Additional connections to wires that you add can be made at any point along the wire. When three or more wires connect at a point the program will place a dot at the connection point as seen in the illustration below.

You will need to add two batteries from the Waveform Sources group of the Analog Primitives menu or from the battery icon at the top of the Micro Cap window before completing the connections. Note that the long line in the battery symbol is the positive end. Each battery should be given the value 15.  The newer versions of Micro-Cap do not need batteries on the diagram.  They create a named voltage source on the text page and give it the default value for power supply voltage for the op-amp being used.  The name of the source is then placed by the power supply terminals of the op-amp.  You can go to the text page and change the value of the source.

You will find the ground connections in the Connectors group of the Analog Primitives menu and on the left end of the component icons at the top of the window. You may have to move some of the components to make room for the batteries, or to make the connections easier. To move or otherwise edit any object in the diagram you must first select the object using the select tool from the tool bar. The select tool is the arrow icon in the upper left corner of the toolbar. Click on this tool, then you can click and drag any object on the screen to a new position. If you click on the component itself then as you drag it to new position its labels move with it. If you click on the label directly then you can move the label relative to the component. This may help to make the diagram more readable when several components are close together. Note the changes in the diagram above compared to the original. Several of the labels have been repositioned. If you wish to remove an object from the diagram then select it and press the delete key. If you wish to change the value of a component then double click on it with the select tool and the properties box will appear and you can change the value of a resistor or the model of an active component such as the Op-Amp. However if you want to change some of the values in the model of a component you must use Ctrl+g to toggle between the circuit window and the model window.