Project Intro

Low-noise amplifier (LNA) is an electronic amplifier used to amplify weak signals captured by an antenna and integrated a low noise figure, reasonable gain, and stability without oscillation over entire useful frequency range. It is usually located close to the detection device to reduce losses gain and input matching in the feed line. This active antenna arrangement is frequently used in microwave system, Global Positioning System, (GPS), because coaxial cable feed line is very loss at microwave frequencies.

A LNA is a key component which is placed at the front-end of a radio receiver circuit. The amplifier needs to have a high amplification in its first stage. Therefore junction Field Effect Transistor (JFETs) and High Electron Mobility Transistor (HEMTs) are often used, and distributed amplifiers could be used. They are driven in a high-current regime, which is not energy-efficient, but reduces the relative amount of shot noise, where shot noise is a noise current mechanism in transistors and diodes. Current flowing in these devices is not smooth and continuous.

An impedance matching network must place between load impedance and transmission line. The need for matching network arises because amplifiers, in order to deliver maximum power to a load, or to perform in a certain desired way, must be properly terminated at both the input and output ports. The matching network is ideally lossless to avoid unnecessary loss power.

A LNA technique presents a considerable challenge because its simultaneous requirement for high gain, low noise figure, good input output matching and unconditional stability at the lowest possible current draw from the amplifier. Although LNA gain, noise figure, stability and input output matching are equally important, they are interdependent and do not always work in each other’s favor.  There are some techniques that used in low noise amplifier (LNA) such as current reuse, folded cascode and PCSNIM with buffer. Current reuse techniques are commonly enables lower current consumption without deteriorating the trans-conductance. Power- constrained simultaneous noise and input matching (PCSNIM) with buffer is a technique evolves from the technique of PCSNIM and simultaneous noise and input matching (SNIM). Thus, the technique used is folded cascode amplifier because it’s suitable for low voltage. It’s called folded cascode amplifier due to its large gain and high bandwidth performances. Although the components and noise are similar to the cascade amplifier, the frequency response and impedance are different. Similar noise performance can be obtained with quite different signal performance and similar to using overall feedback to have low noise and still optimize signal performance.

In this project, the capability of gain, noise and input output matching are measured. The performance of folded cascode technique also investigated even thought it has low linearity and high power consumption.