Impacts of the Pads, ESD Diodes and Package Parasitic on the Noise Figure and Gain of a Common Source Low Noise Amplifier

The impacts of the pads, ESD diodes, wirebonds and package parasitic on the noise figure of a common source low noise amplifier (LNA) are studied. For the general case a common source LNA without the source degeneration inductor has been considered. An electrical model for quad flat nonleaded (QFN) package is presented and used to examine the effects of package parasitic. Equations of input impedance and transconductance of the LNA are derived. Effects of the pads, ESD diodes, package parasitic and input matching components on the gain and noise figure for power constrain optimization technique are highlighted.