Output-Conductance Transition-Free Method for Improving the Radio-Frequency Linearity of Silicon-on-Insulator MOSFET Circuits

In this paper, a novel concept is introduced to improve the radio-frequency (RF) linearity of partially depleted (PD) silicon-on-insulator (SOI) MOSFET circuits. The transition due to the nonzero body resistance (R \(_{\rm Body}\) ) in output conductance of PD SOI devices leads to linearity degradation. A relation for R \(_{\rm Body}\) is defined to eliminate the transition and a method to obtain transition-free (TF) circuit is shown. 3-D numerical analysis of body-contacted devices is carried out to extract the TF body resistances. To identify the output conductance TF concept and its application to RF circuits, a 2.4-GHz low-noise amplifier (LNA) is further analyzed. Mixed-mode device-circuit analysis is carried out to simultaneously solve device carrier transport equations and circuit SPICE models. Fast Fourier transform calculations on the output signal are performed to compute harmonic distortion figures. Comparing the conventional body-contacted (CBC) and TF SOI LNAs, third harmonic distortion and total harmonic distortion (THD) are improved by 16% and 24%, respectively. Two-tone test is used to analyze third-order intermodulation distortions. Third-order output intercept point is improved in TF SOI LNA by 17% comparing with that of the CBC SOI LNA. The results demonstrate superior advantage in application of TF design concept to SOI MOSFET circuits.

I. Introduction

Silicon-on-insulator (SOI) MOSFETs are commonly utilized for digital, radio frequency (RF), and analog integrated circuit applications. Partially depleted (PD) SOI MOSFET is the main SOI architecture for RF solutions. Since the active silicon film layer is electrically insulated, floating-body effects (FBEs) are normally observed in PD SOI MOSFETs [1]. The kink that is associated with FBEs is frequency dependent and vanishes at RF operating range. However, it is essential to connect the device body to an external voltage for RF applications [2]. Body-contacted devices are required to avoid body voltage variations and obtain proper device matching.