RF and Microwave Circuit and Component Design for Wireless Systems

CHAPTER EIGHT

Low-Noise Amplifiers

8.1 INTRODUCTION

Rapid development of personal communication system over the last decade has led to the development of low cost, better performing low-noise amplifiers. Low power consumption receivers are necessary to increase talk time of wireless communication products. Long battery life, less weight, small size, and low cost are some of the key parameters that determine the success of a portable communication product. To meet the customer demand for longer talk time, low power receiver ICs and high-efficiency power amplifiers are being designed into wireless communication products. A receiver system for the portable communication application consists of the following circuits: a low-noise amplifier, mixer, VCO, IF amplifier, and filters. Semiconductor devices with better noise-figure-gain performance are needed to maintain the same RF performance at lower voltages. Highly linear devices and circuits are needed for digital wireless systems. Front-end circuits with good performance have been fabricated using silicon bipolar, silicon BiCMOS, GaAs MESFET, HFET, HBT, and SiGe technologies. In this chapter we will discuss the low-noise amplifier design fundamentals, with special emphasis on low-power communication circuits.

8.2 TWO-PORT DESCRIPTION OF A DEVICE

RF circuit designers have plenty of choices for devices in the market place. Selection of a device for a particular application is a challenging task. A designer typically starts with the analysis ...