LOW NOISE CONSIDERATIONS

The noise figure, NF, of an amplifier is defined by the equation:

 

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An ideal amplifier should amplify the incoming signal and noise without changing the signal-to-noise ratio, that is, the noise figure would be unity (i.e. 0 dB). In practice, some extra noise is generated in the transistor and so the noise figure of a transistor amplifier is always greater than unity. The nearer the noise figure is to unity, the better is the amplifier.

If an amplifier is required to amplify signals with amplitudes of the order of microvolts, special attention must be paid to the design from the low noise aspect. The noise figure ...

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