Low-noise amplifier

low noise amplifierLNAlow noise receiverslow-noise amplificationlow-noise audio designspre-amplifiersRF amplifier
A low-noise amplifier (LNA) is an electronic amplifier that amplifies a very low-power signal without significantly degrading its signal-to-noise ratio.wikipedia
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Signal-to-noise ratio

signal to noise ratioSNRsignal-to-noise
A low-noise amplifier (LNA) is an electronic amplifier that amplifies a very low-power signal without significantly degrading its signal-to-noise ratio.
Additionally, internal noise of electronic systems can be reduced by low-noise amplifiers.

Noise figure

noise factorreceiver noise
A typical LNA may supply a power gain of 100 (20 decibels (dB)) while decreasing the signal-to-noise ratio by less than a factor of two (a 3 dB noise figure (NF)).
For this reason, the related figure of effective noise temperature is therefore often used instead of the noise figure for characterizing satellite-communication receivers and low-noise amplifiers.

Amplifier

amplifiersamplificationelectronic amplifier
A low-noise amplifier (LNA) is an electronic amplifier that amplifies a very low-power signal without significantly degrading its signal-to-noise ratio.

Antenna (radio)

antennaantennasradio antenna
Antennas are a common source of weak signals.
Antenna gain should not be confused with amplifier gain, a separate parameter measuring the increase in signal power due to an amplifying device placed at the front-end of the system, such as a low-noise amplifier.

Coaxial cable

coaxialcoax cablecable
An example is a feed line made from 10 feet of RG-174 coaxial cable and used with a global positioning system (GPS) receiver.
Coax cable is often used to carry data/signals from an antenna to a receiver—from a satellite dish to a satellite receiver, from a television antenna to a television receiver, from a radio mast to a radio receiver, etc.In many cases, the same single coax cable carries power in the opposite direction, to the antenna, to power the low-noise amplifier.

RF front end

front endfrontendradio front ends
In most receivers, the overall NF is dominated by the first few stages of the RF front end.

Friis formulas for noise

Friis equationFriis formulaFriis' formula
Friis' formulas for noise models the noise in a multi-stage signal collection circuit.
For this reason, the first stage amplifier in a receiver is often called the low-noise amplifier (LNA).

Field-effect transistor

FETfield effect transistorfield-effect transistors
The transistor may be one of many varieties of bipolar transistors or field-effect transistors.
Because base current noise will increase with shaping time, a FET typically produces less noise than a bipolar junction transistor (BJT), and is found in noise-sensitive electronics such as tuners and low-noise amplifiers for VHF and satellite receivers.

Common emitter

common-emittercommon-emitter amplifieremitter degeneration
For a medium source impedance, a common emitter or common source topology may be used.
Common emitters are also commonly used as low-noise amplifiers.

Noise (electronics)

noiseelectronic noiseelectrical noise
An amplifier will increase the power of both the signal and the noise present at its input, but the amplifier will also introduce some additional noise.

Radio

radio communicationradio communicationswireless
LNAs are found in radio communications systems, medical instruments and electronic test equipment.

Electronic test equipment

test equipmentelectronic test instrumentelectrical test equipment
LNAs are found in radio communications systems, medical instruments and electronic test equipment.

Power gain

A typical LNA may supply a power gain of 100 (20 decibels (dB)) while decreasing the signal-to-noise ratio by less than a factor of two (a 3 dB noise figure (NF)).

Decibel

dBdecibelsbel
A typical LNA may supply a power gain of 100 (20 decibels (dB)) while decreasing the signal-to-noise ratio by less than a factor of two (a 3 dB noise figure (NF)).

Noise floor

floornoise-floor
Although LNAs are primarily concerned with weak signals that are just above the noise floor, they must also consider the presence of larger signals that cause intermodulation distortion.

Intermodulation

intermodulation distortioncross modulationintermodulation product
Although LNAs are primarily concerned with weak signals that are just above the noise floor, they must also consider the presence of larger signals that cause intermodulation distortion.

Transmission line

transmission linestransmissiontransmission-line
An outdoor antenna is often connected to its receiver by a transmission line called a feed line.

Feed line

feedlinefeeder linefeeding line
An outdoor antenna is often connected to its receiver by a transmission line called a feed line.

Standing wave ratio

VSWRSWRvoltage standing wave ratio
Further specifications are the LNA's operating bandwidth, gain flatness, stability, input and output voltage standing wave ratio (VSWR).

JFET

junction field-effect transistorjunction gate field-effect transistor(JFETs)
Therefore, junction field-effect transistors (JFETs) and high-electron-mobility transistor (HEMTs) are often used.

High-electron-mobility transistor

HEMTHigh electron mobility transistorHFET
Therefore, junction field-effect transistors (JFETs) and high-electron-mobility transistor (HEMTs) are often used.

Shot noise

Poisson noiseshotshot-noise
They are driven in a high-current regime, which is not energy-efficient, but reduces the relative amount of shot noise.

Narrowband

narrow-bandnarrownarrow band
It also requires input and output impedance matching circuits for narrow-band circuits to enhance the gain (see Gain-bandwidth product).

Gain–bandwidth product

gain-bandwidth producttransition frequency high-frequency operating characteristics
It also requires input and output impedance matching circuits for narrow-band circuits to enhance the gain (see Gain-bandwidth product).

Radio receiver

receiverreceiversRadios
An LNA is a key component at the front-end of a radio receiver circuit to help reduce unwanted noise in particular.