Performance and Characteristics of Ultra Low Noise Amplifiers

This white paper describes the performance and characteristics of two new ultra low noise LNAs from Skyworks. Topics include techniques used in biasing and matching these devices. A circuit description, including information on thermal considerations, is also addressed. This family of products presented here are ultra-high-performance, low noise single stage amplifiers designed for wireless applications in the 30 MHz to 4 GHz range.

The primary function of the LNA is to minimize the cascaded noise figure of the receiver. According to the Friis equation, the LNA gain minimizes the cascaded NF impact of subsequent stages and its low NF minimizes its own NF contribution. This resulting low cascaded NF results in optimal receiver sensitivity in low signal level conditions and thus the LNA is a common receiver element in the vast majority of receiver architectures. In addition to its gain and NF characteristics, the LNA linearity should also be high enough so that this stage does not limit the cascaded IIP3 and the P1dB of the receiver.