Linearity improvement of LNA using Derivative Superposition: Issues and challenges

LNA being the first block of all RF receiver systems, demands very large gain and low noise with high linearity. Lots of techniques are available to increase the gain and reduce the noise contribution of LNA. Linearity of LNA has started grabbing attention of researchers as transistor size reduces and frequency of operation goes to the microwave range. Traditional techniques of linearity improvement may not work with higher gain requirements. Derivative Superposition (DS) is one of the new methods, which seems promising for the improvement in Linearity of LNA. The paper covers the concept of DS. The issues with the simple DS method are discussed and possible improvements in the design are suggested. The challenges for each design are also presented. LNA designs using DS with possible variations are implemented and compared for Gain, Power requirement and Linearity.