An amplifier takes small electrical signals and makes them into bigger ones (gain)..amplifying a range from microvolt signals boosting to millivolts or boosting millivolts to volts. Well designed low-noise amplifiers have a high S-N ratio (signal to noise).
Low noise amplifiers do so with little or no introduction of noise (unwanted signals such as spurious signals from RF (Radio Frequencies or trash signals). They can do so with the help of well-shielded and well grounded inputs. Generally such amplifiers are designed and used for audio purposes but not always. Frequent use also is in space satellites for communications.
Your question is vaguely worded so perhaps you can be more specific as to what sort of answer you're looking. What do you mean by components?
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