Audio News

Low noise amplifiers, most commonly known as LNAs, make up the basic building block of the communication and are specially designed for amplifying weak signals captured by the antenna to the acceptable levels while minimizing the noise. These amplifiers have to be placed very close to the antennas to make the losses in the feedline less critical.

The LNA reduces the noise of all the consecutive levels and finally injects the absolute noise of the LNA directly into the received signal. Therefore, it is quite essential for a Low Noise Amplifier to enhance the desired power of the signal, while adding as little noise and distortion as possible. That way the signal can be retrieved easily in the later stages in the system.

The LNA should deliver as a high amplification as possible at the initial stage, so as to have less distortions and noise later. HEMT (High Electron Mobility Transistor) and JFET (Junction Field Effect Transistor) help in providing a solution to this problem. These amplifiers are often located in radios, such as the Sony XDRS10DAB, at the front end of the radio receiver circuit. These amplifiers are also usually operated with a high current, which is definitely not energy efficient, but helps in reducing the relative amount of shot noise. Matching circuits for the input and output are used so as to increase the gains. The use of resistors is avoided or at least restricted, as they only help in adding up the unwanted noises.

We all know that noise signals are typically low level signals and virtually unavoidable in any measurement system. Therefore we require preamplifiers like the LNA, which have sufficient sensitivity to measure these noise signals and offer premium performance.