Cadence Symbol Creation- Legacy

The symbol editor lets you create a "black box" description of a cell using labels, pins, shapes, notes, and a selection box. Symbols make your design more readable, as you can use them in more complex designs, instead of individual transistors.

• In the Library Manager, highlight the Cpe_311_AMI06 library.

• Go to File >New Cell. In the Cell Name type nmos_inv and specify the Type as SchematicSymbol.

• The Virtuoso Symbol Editing window should appear.

• You are ready to draw a symbol for the inverter. First, we will draw a triangle to represent the inverter body. Left click Editing: Create > Shape > Polygon

• To draw a polygon, click at a start point, and then click at the corners of the shape you want to create. To finish the polygon, click again on the start point. Since we are drawing an inverter, we need a sideways triangle, so make one of those.

• The inverter needs a negation circle at the sideways corner of the triangle, so left click Create > Shape > Circle. Left click at the point you want to be the center of the circle. Move the mouse until the circle is the size you want, and left click again.

• Click Create >Shape >Line. Now draw a line that starts at the middle of the vertical line of the triangle and ends somewhere to its left and another line from the rightmost part of the circle to somewhere equally to the right.

• Now, you want to add pins to the symbol. Left click Create > Pin. In the Pin Names box type the following pin names: Vin. Also change the direction of the pins to Input for Vin and Output for Vout. Add the Vin pin on the left of the symbol and the Vout pin on the right of the symbol.

• Next we want to add label to the symbol. Left click Create > Label. The Add Symbol Label dialog box should appear. We will add an instance label. Just left click the Hide button, and place the label somewhere near the symbol of the inverter.

• Next, we will add a label to the symbol which will describe the circuitry. In this case, the label will be nmos_inv for inverter. In the Add Label window type INV in the Label field as shown in the figure below:

• The last thing to add is a selection box. This will tell the software how much of the symbol is actually used. Left click Create > Selection Box. Left click the Automatic button.

• The symbol is now finished and you can save it by clicking on the save button. The symbol should look like the one below: