Selection of Optimum Device Size and Trans-Conductance Ratio for High Speed Digital CMOS Inverter Design for a Given Fanout Load

The PMOS/NMOS width ratio (ß) and W/L ratio of NMOS device is an important ratio in the design of digital logic cells using conventional CMOS logic design style. In this paper we propose a simulation-based method applied to CMOS inverter to accurately estimate an optimum W/L ratio of NMOS device and PMOS/NMOS width ratio when fanout loading of 1, 4 and 8 cells of similar type are present. The appropriate selection of W/L ratio of NMOS device and PMOS/NMOS width ratio makes the digital design faster and reduces the power consumption.