Wideband LNA Using a Negative gm Cell for Improvement of Linearity and Noise Figure

Abstract

A differential common gate low noise amplifier (LNA) has been widely used for a wideband LNA. However, it has poor linearity due to a nonlinear transconductance in a MOSFET and poor noise performances from the common gate configuration. We propose a differential common gate LNA with a negative g m cell for the improvement of the linearity and noise figure. The cell comprises cross coupled transistors instead of a current source. The negative g m cell creates the opposite phased harmonic, canceling the distortion. The noise figure is improved by canceling the noise from the common gate transistors through the negative g m cell. The LNA is fabricated in 0.13 μm RF CMOS. The LNA has the bandwidth of 0.7 ∼ 3.5 GHz frequency and has provided the expected characteristics for linearity and noise figure.