An analysis of the kink phenomenon of scattering parameter S22 in RF power mosfets for system-on-chip (SOC) applications.

In this paper, the kink effect in scattering parameter S22 of RF power MOSFETs with drain-to-spacer offset is explained quantitatively for the first time. Our results show that for RF power MOSFETs the output impedance can be represented by a “shifted” series RC circuit at low frequencies and a “shifted” parallel RC circuit at high frequencies. The appearance of the kink point of S22 in a Smith chart is caused by this inherent ambivalent characteristic of the output impedance. It is found that an increase of drain-to-spacer offset enhances the kink effect. In addition, the kink effect in S22 of RF power MOSFETs can also be interpreted in terms of poles and zeros. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 36: 371–376, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10767 [ABSTRACT FROM AUTHOR]