Influence of Layout Parasitics on EMI Improved Folded Cascode Amplifier Input Stages Using Filtering and Linearisation Methods

This paper investigates the electromagnetic interference (EMI) behaviour of EMI improved integrated folded cascode amplifier input stages. In this context three EMI improved differential input pair structures, using concepts of filtering and linearisation, are compared in terms of their susceptibility. Special attention is paid to the differences in the behavior of the structures at the design stage and the layout stage, where layout-specific parasitics that can affect circuit performance are also considered. Comparisons on the investigated structures are made in terms of EMI induced offset voltage, electromagnetic interference rejection ratio (EMIRR), layout considerations, differential and common mode gain, gain-bandwidth product (GBWP), stability, power consumption, area requirement (estimation vs. implementation) etc.