- What:
- For a receiver, NF indicates the ability to discriminate the desired signal from background noise.
- Good IC LNAs tend to have NFs in the 1 - 3 dB range; for better noise performance a tuned discrete transistor (often a MESFET or PHEMT) is typically required. For ICs intended for use as gain or power stages the NF will typically be in the 7 -10 dB range. NF increases with frequency and to a first order increases with bias.
- Direction:
- NF really only matters when the device is used in a receiver and in a location where there is not a lot of gain in front of it (the noise contribution of a device is divided by the gain in front of it). Then lower is better.
- Range:
- 1.5 - 10 dB (for lower noise figures, use a discrete transistor)
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