Low Noise Amplifier DesignSession 8Introduction of Noise(A)High Frequency Noise1.Thermal (Johnson or Nyquist) noise1.Thermal vibration of bound charges.2.Shot noiseRandom fluctuations of charge carriers.(B)Low Frequency NoiseFlicker (1/f) noiseNoise power varies inversely with frequency.LNA cares high frequency noise only!2Noise Factor and Noise Figure of AmplifierSiSo=GSiNiNo=GNi+NSi= Input signal powerSo= Output signal powerNi= Standard input thermal noiseNo= Total output noise powerN= Amplifier excess noise powerG= Amplifier power gain Noise factorNoise figure(Ni=kT0B=-174dBm/Hz+Bandwidth(dBHz) T=T0=290K)3Noise Figure of a Two-Port NetworksNoise Parameters: (4 values)Fmin : Minimum noise factor S= minrn= Rn/Z0 : Normalized noise resistancemin=|min|qmin Minimum-noise source reflection coefficient F= Fmin4Noise Parameters of the TransistorGaAs FET ATF-10136 Noise ParametersBiasdependentFrequencydependent5Noise Parameters from Linear Model! SIEMENS Discrete & RF Semiconductors! BFP420! Si NPN RF SIEGET Grounded Emitter Transistor in SOT343! VCE = 1 V IC = 1.5 mA ! Common Emitter S-Parameters: February 1998# GHz S MA R 50! f S11 S21 S12 S22! GHz MAG ANG MAG ANG MAG ANG MAG ANG 0.010 0.9253 -0.9 5.283 179.7 0.0013 94.7 0.9962 -0.5 0.100 0.9234 -7.4 5.274 174.7 0.0117 85.7 0.9935 -4.11.000 0.8120 -72.4 4.363 126.8 0.0972 48.1 0.8140 -37.32.000 0.6826 -129.4 3.080 88.7 0.1318 21.7 0.5819 -60.93.000 0.6464 -171.6 2.264 61.1 0.1373 6.7 0.4292 -76.24.000 0.6509 155.6 1.748 38.1 0.1339 -2.2 0.3584 -96.25.000 0.6888 132.5 1.389 18.6 0.1269 -7.3 0.3011 -115.36.000 0.7115 116.0 1.148 1.5 0.1241 -7.7 0.3095 -142.2! ! f Fmin Gammaopt rn/50! GHz dB MAG ANG - 0.450 0.71 0.32 21 0.35 0.900 0.76 0.51 34 0.27 1.800 1.07 0.36 78 0.20 2.400 1.17 0.36 97 0.19 3.000 1.43 0.37 132 0.12 4.000 1.70 0.41 -173 0.09! SIEMENS AG Semiconductor Group, MunichTouchstone-format S-parameters with noise data6Noise Parameters from Nonlinear ModelNonlinear Transistor ModelDetermine Biasing CircuitsSmall Signal AnalysisNoise measurementsOptimum Noise Figure Match: GMN Minimum Noise Figure: NFMin Noise Resistance: RN 通常其結果準確度不一定足夠，僅供設計時參考！7Constant Noise Figure Circles of TransistorLet F= Fi Fmin|S- CFi| = rFi為S-Plane上的圓方程式，並稱之為constant noise figure circle圓心半徑where8Constant Noise Figure Circles of TransistorNFminminNFmin-1dBS-PlaneNFmin-2dBNFmin-3dBrn越大，當遠離min時NF上升越快。9Noise Circles v.s. Available Gain Circles兼顧NF and GA亦即兼顧VSWR1Trade-off is needed!MSminNFGAS-Plane10Inductor Series Feedback MethodBFP420 (IC=1.5mA, VCE=1V) f=2GHzStabilizing loadEmitter feedback inductor11Inductor Series Feedback MethodLE= 0 nHLE= 0.8 nHLE= 2.4 nH增加LE可以讓MS與min接近，同時達到較低的雜訊及良好的input matching。但負回授會降低增益。MSmin12部分资料从网络收集整理而来，供大家参考，感谢您的关注！