Performance analysis of high-speed MOS transistors with different layout styles

Several layout schemes for MOS transistors have been investigated and compared in terms of speed and layout area. Among them, the so-called closed, donut or doughnut transistors have been characterized, obtaining an analytical expression for the calculation of the equivalent W/L ratio for a general n-side regular polygonal-shape. The comparisons show that with quasi-minimum dimension transistors and L=0.35 mum, reductions of up to 81% on the drain area can be achieved with an increase of only a 10% on the total layout area for given W and L. An application improving the switching speed of an output multiplexer is shown.