Low Noise Amplifier Design

This chapter presents a design procedure to design a stable low noise amplifier based on linear design techniques. It introduces some important definitions used in the design theory of linear radio frequency and microwave amplifiers. Signal amplification is a fundamental function in all wireless communication systems. Amplifiers in the receiving chain that are closest to the antenna receive a weak electric signal. Noise circles in combination with gain circles are efficient aids for circuit designers when optimizing the overall amplifier circuit network for low noise with high associated gain. A systematic mathematical solution, aided by graphical methods, is developed to determine the input and output matching network for a particular noise, gain, stability, and gain criteria. Multiple gain stages complicate the design considerably. Negative feedback is widely used in amplifier design to stabilize gain against parameter changes in the active device due to supply voltage variations and temperature changes.