What makes a good low-noise device?

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What makes a good low noise device?  Ideally, you want to optimizeall  noise parameters:  GammaOpt should be close to the conjugate match at your operating frequencies. RN should be as large as possible to provide a "soft" fall-off as your matching network moves away from Gamma_opt.

Choice of device type: GaAs pHEMT is better than SiGe HBT

Geometry: Multiple gate fingers lower the gate resistance. Certain peripheries may have hold teh advantage of gamma opt for noise figure being closer to conjugate match.

Dissipation: large devices cause more heat raising channel temperature.

Bias point: Usually a low voltage just pass the knee of teh curve is going to give the lowest NFmin, with current well below Class A.

Intrininsic properties: if your process has any gate leakage at all, it will show up in noise figure.

Here's a wite paper from NXP that provides much more detail on LNA design.





Author : Unknown Editor