WIDEBAND LNA USING A NEGATIVE g(m) 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 mu m RF CMOS. The LNA has the bandwidth of 0.7 similar to 3.5 GHz frequency and has provided the expected characteristics for linearity and noise figure.