A MOS Model 9 Extension for GHz CMOS RF Circuit Design

This paper presents an extension to the compact MOS model 9 that enables accurate simulation of CMOS RF circuits in the GHz range. The MOS model 9 is generally accepted for low frequency design, but it is quite inaccurate at GHz frequencies if device parasitics are not considered. The presented model is based on a MOS model 9, extended by a network of parasitics, consisting of six resistors, five capacitors, and two JUNCAP diode models. A model developed for a 0.25 μm CMOS technology shows good accuracy in the measured frequency range up to 12 GHz and over a wide bias range. By applying simple rules for scaling of parasitics and a unit transistor layout approach, the model also shows scalability with respect to device width. The model also predicts third-order intercept point with good accuracy, and simulations and measurements on a 2 GHz CMOS amplifier shows also good agreement.