A Physical Interpretation of the Distance Term in Pelgrom’s Mismatch Model results in very Efficient CAD

Abstract

In 1989 Pelgrom et al. published a mismatch model for MOS transistors, where the standard quadratic deviation of the mismatch in a parameter between two identical transistors, is given by two independent terms: (1) a transistor size-dependent term and (2) an inter-transistor distance-dependent term. To include the distance term, some researchers have developed CAD tools based on the so called σ-Space Methodology, which result in very computationally expensive algorithms. Such algorithms become non-viable even for circuits with a reduced number of transistors. On the other hand, by understanding and interpreting correctly the physical origin of Pelgrom’s model distance term, one can implement in a straight forward manner this mismatch contribution in a CAD tool. Furthermore, the computational cost results negligible and viable for any number of transistors.