Draw layout of six transistor CMOS SRAM using lambda rule
1 Answer


  • Static latches are used in the SRAM cell. SRAM cell is made up of flip flop comprising of two cross coupled inverters.

  • Generally this word line is connected to the output of row decoder circuits. When WL=VDD the SRAM cell is connected to bit line(BL) and complement of bit line (BLbar) allowing both read and write operations.

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  • Design rules include geometric constraints and line width constraints.

  • The later defines constraints like metal and polysilicon interconnection, diffusion area, minimum feature dimensions and allowable separations between two different features.

  • They are known as lambda rules.

  • In micron rule all layout constraints are defined in micrometers while in lambda rule it is defined in terms of a single parameter lambda (λ).

  • For the SRAM cell layout shown in the Figure first we need to design the individual transistors according to the design rules.

  • From the layout Figure it can be noted that total area of the SRAM cell can be further reduced by using optimization methods. Since. basic motto of this SRAM cell design is to understand the layout methodology no optimization effort is put.

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