Tutorials:Cadence:CreatingSchematicTransistorIV

Creating Schematic for Transistor Testing

Click Library Manager: New → Cell View...

The New File form should appear as shown below. We will be making a test transistor schematic, so type test_transistor in the Cell field. In the View field type schematic or from the Type pull-down menu choose schematic and the View field will be automatically filled. In the Application section, select the following: Open with Schematic XL and check the box next to Always use this application for this type of file. Once you make these two selections, in the future they will be automatically selected.

Left click the OK button.

The Virtuoso Schematic Editor window should be showing on your screen as shown in the figure below:

Left click: Schematic Editor: Create → Instance... (bind key <i>)

Shortcuts: You may notice letters by some of these menu choices. Rather than clicking through all the menus, you can just hit that button on the keyboard to the same effect. These are called bind-keys. In the future, you can press <i> in order to insert an instance.

A Command Browser window appears. In this window, select NCSU_Analog_parts under Library pull down menu. Next click on N_Transistors → nmos4. The window should look as shown in the figure below:

Once you select nmos4, an Add Instance window appears. Type nmos4 to choose a four terminal NMOS transistor in the Cell box and symbol in the View box. Note that you can use the Browse button in order to browse through the libraries and find the cell you want. You can edit the parameters of the nmos4 cell, such as width, length, etc. For this exercise, keep the default parameters. The Add Instance window is shown in the figure below.

Move the cursor into the editing window. Notice that there is a NMOS transistor there instead of the normal cursor. Position it where you want to put the transistor, and left click to place it. You can right click to rotate the transistor if you want it to face a different direction (this is especially useful with pins). While placing, moving, stretching, etc., you can press F3 to show the options form for the command if it is currently hidden.

Press <Esc> to return to a normal cursor after you have finished placing all the transistors you want. For this inverter example, place it on the bottom half of the screen on the right side of the center-line. To rotate press <r>.

To make life easier: Before trying to place a component, left click the Hide button on the Add Component window. This will move it into the background so it's out of your way.

Now we want to add voltage DC sources. Left Click Schematic Editor: Create → Instance.... In NCSU_Analog_Parts library, under Voltage_Sources category, you will find the vdc source. Place it in the test circuit. The Component Browser should look like the one below:

Select Vdc. The Add Instance window will appear. In the DC Voltage field enter 5V (note, the "V" is automatically added when you tab off of the field). This window should appear as such:

Place the symbol to the left of the transistor. Now we want to add ground lines. Left click Schematic Editor: Create → Instance.... In NCSU_Analog_Parts library, under Supply_Nets category, you will find gnd symbol. Place it in the test circuit. The Component Browser should look like the one below.

Once you select the gnd symbol, the Add Instance window for gnd should look like the one below:

Now, we'll add all the wires to make the circuit work. Left click Schematic Editor: Create → Wire (bind key <w>). The Add Wire form should appear. Just click its Hide button. You can refer to the figure below to see how everything is connected together.

Notice that as you get closer to one pin than another (including those on devices), a small diamond will show up inside of or around that pin. That is where you want to click to connect a wire. Also, when wiring the schematic, leave the wire width at 0, Route method at full, and (usually) Draw Mode as route. This tells the software to auto-route the wires for you. If you put a wire where you don't want it to go, you can delete the wire by left clicking Schematic Editor: Edit → Delete (bind key <del>) and then left click on the object you want to delete (wire, pin, component, etc.).

A picture of what the circuit should look like is shown below:

Once you are done editing, left click the "check mark" icon on the left side of the screen. This will check your work for connection errors and will save your work in the library. You can accomplish the same thing by left clicking Schematic Editor: File → Check and Save.

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