Introduction to VLSI Design

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Example: CMOS Inverter Layout

Power Rails


Now that our transistors are placed and connected, we will have to add Power and Ground rails. Usually a layout consists of a large number of cells, all of which need power and ground connections. Therefore it is common to design cells such that they will have one continous, wide power and ground connection when placed side by side.

Our Signal Flow Graph suggests horizontal power and ground lines in Metal-1.

1. Draw the Power Rail in Metal-1 above the PMOS

Click to enlarge

2. Draw the Ground Rail in Metal-1 below the NMOS

Click to enlarge

Make sure to connect the Power Rail and the Ground rail to the source contact of the PMOS and to that of NMOS, respectively.



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Last Updated by Ilhan Hatirnaz on 11/7/1998