Amplifiers amplify signals. Decibels (dB) is the unit used to measure signal boost or gain. Amplifiers can be classified as:

• Everything else.

Low-noise amplifiers (LNAs) are connected to antennas to enhance the received signal such that it can be identified by the electronics of the RF system to which it is connected to. Additionally, they are also evaluated for noise factor. Noise factor can be defined as a measure of external noise introduced to the signal. Smaller noise factors enable the receiver to observe smaller signals, thereby permitting greater range.

High-power amplifiers (HPAs) are utilized to enhance a signal to the maximum degree of power prior to transmission. The unit for measuring output power is dBm (dB relative to 1 mW). Amplifiers radiate heat in addition to amplifying the signal. This is because amplifiers are dependent on thermodynamic laws.

The transmitter present in an 802.11 PC card is low power because it is essential that it runs off a battery if it is installed in a laptop. However, it is possible to install an external amplifier at access points, which can then be connected to the power grid.

802.11 devices are restricted to 1 W of power output and 4 W effective radiated power (ERP). ERP multiplies the transmitter's output power by the antenna gain minus the loss in transmission line. So essentially, if we have a 1-watt amplifier, an antenna that provides 8 dB of gain and 2 dB of transmission line loss, then it results in an effective radiated power (ERP) of 4 W. The total system gain is 6 dB, which multiplies the transmitter's effective power by a factor of 4.

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