An optimized output stage for MOS integrated circuits

Abstract

An output device for optimizing propagation delay and minimizing chip area is described. An optimum means of tapering the output stages to minimize propagation delay is determined. The minimum delay is a function of the capacitive load to node ratio, the number of output stages, and the interstage propagation delay. The effects on area are also presented. A figure of merit which is a function of area and propagation time is defined which is of use in designing output stages. An optimum exists which can be considered the best compromise between further decreasing propagation delay and increasing chip area. Data are also presented which allow a designer to determine the minimum chip area once the capacitive load and the maximum allowable delay are known.