=== Gain===

An amplifier’s output/input magnitude ratio is gain. In RF, the gain is generally specified in logarithmic scale (dB).

=== SNR (Signal to Noise Ratio) ===

The ratio of signal power to the noise power, often expressed in decibels.

=== NF (Noise Figure) ===

It is measures of degradation of the SNR, caused by components in a RF signal chain.

=== Bandwidth ===

Noise figure of a component has been defined above. But one can also define the noise figure of a system consisting of multiple components connected in series. NF of this kind of system is define in a very similar way as above with SNRin is the SNR of input to the system and SNRout is the SNR of the output of the system. <br \>

If we know the individual noise figures, we can calculate the noise figure of the system using this formula,

=== Need of LNA ===

* '''Matching Circuits:''' The input and the output must be matched to 50ᘯ for optimal performance. Every device has a Input and output impedance. These are the impedances looking from input and output respectively. For maximum transfer of power all the impedances of connecting components or tracks or wires should be same. If there is a mismatch the signals may get reflected and damage the amplifier. For more reading one can read Transmission lines. <br \>

If there is a mismatch between input of a connected device and output of the other device and matching circuit has to be designed for impedance matching. Example is shown in the following figure.

== Power Amplifier (PA) ==

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