Abstract

Low-noise amplifiers (LNAs) are critical components to any modern electronic communications system. LNAs are usually placed at the beginning of a multistage system and are designed with high gain to suppress the noise contributions of subsequent stages. Aside from noise and gain, other performance criteria such as, distortion effects, power consumption, and circuit size have varying degrees of importance based on the LNA's destined application. It is the way in which the LNA is designed ( i.e. topology selection, design methodology, fine-tuning, etc.) that will determine how well the LNA performs. Currently, there is no unique or systematic approach for the design of these relatively complex circuits. Hence, the development of CAD tools for LNA design is an attractive alternative to traditional pen and paper approaches. This thesis can be divided into two main parts; computer aided LNA design from an analog perspective and computer aided LNA design from a RF/microwave perspective. Analog engineers tend to work with traditional electronic components ( e.g. transistors, resistors, inductors, capacitors, etc.). In this work, a computer aided approach is devised which performs appropriate topology selection, design, and fine-tuning. In the RF/microwave world, designers tend to work at higher operating frequencies, and thus use microwave oriented components such as micro-strips and waveguides. Given the S -parameters for a specified transistor, the proposed approach finds an input/output reflection coefficient that maximizes the LNA gain for a specified noise-figure. The proposed CAD approach exploits "constrained line search optimization" to increase the accuracy of the LNA circuit and to reduce the time needed in the design process. The CAD approaches are illustrated via practical LNA examples. The resulting LNA designs are shown to have improved performance w.r.t the user-specifications.