MIT Virtual Source RF Model as a Tool for GaN-Based LNA and Oscillator Design

This work demonstrates the usefulness of the physics-based MIT Virtual Source GaNFET (MVSG) model in the design of GaN based RF low noise amplifiers (LNAs) and oscillators. The model with its accurate representation of small and large signal device characteristics along with RF- and low frequency noise behavior can be used for the design of LNAs with the required noise figure (NF) and oscillators with the desired frequency response including the close-in phase noise performance. The MVSG model is benchmarked against device terminal DC-, small-signal S-parameter- and noise figure measurements and is used to design an LNA with antenna switches, which achieves 3.7 dB NF with 12 V supply voltage at 5.9 GHz (IEEE 802.11p standard) [1]. A 3-stage GaN pseudo-invertor ring oscillator, delivering 21 dBm at 1.4 GHz is designed using the MVSG model to determine its accurate estimation of large-signal device-switching behavior along with the device- flicker (1/f) noise-dominated phase noise. The dependence of phase noise level on the DC component of the impulse sensitivity function (ISF) [2, 3] is confirmed using the model and measurements. In this work, the physics of carrier charge and transport in a GaN-HEMT along with device-level noise is translated into functional RF-circuit elements using the MVSG model.