《《低噪声放大器简介》ppt课件》由会员分享，可在线阅读，更多相关《《低噪声放大器简介》ppt课件（115页珍藏版）》请在金锄头文库上搜索。
1、Low-Noise Amplifier,RF Receiver,BPF1,BPF2,LNA,LO,Mixer,BPF3,IF Amp,Demodulator,Antenna,RF front end,Low-Noise Amplifier,First gain stage in receiver Amplify weak signal Significant impact on noise performance Dominate input-referred noise of front end Impedance matching Efficient power transfer Bett
2、er noise performance Stable circuit,LNA Design Consideration,Noise performance Power transfer Impedance matching Power consumption Bandwidth Stability Linearity,Noise Figure,Definition As a function of device G: Power gain of the device,NF of Cascaded Stages,Overall NF dominated by NF1 1 F. Friis, “
3、Noise Figure of Radio Receivers,” Proc. IRE, Vol. 32, pp.419-422, July 1944.,Sin/Nin,G1, N1, NF1,Gi, Ni, NFi,GK, NK, NFK,Sout/Nout,Simple Model of Noise in MOSFET,Flicker noise Dominant at low frequency Thermal noise g: empirical constant 2/3 for long channel much larger for short channel PMOS has l
4、ess thermal noise Input-inferred noise,Vg,Id,Vi,Noise Approximation,Thermal noise,1/f noise,Band of interest,Frequency,Noise spectral density,Thermal noise dominant,Power Transfer and Impedance Matching,Power delivered to load Maxim available power,Rs,Vs,jXs,jXL,RL,I,V,Impedance matching Load and so
5、urce impedances conjugate pair Real part matched to 50 ohm,Available Power,Equal power on load and source resistors,Reflection Coefficient,Rs,Vs,jXs,jXL,RL,I,V,Reflection Coefficient,No reflection Maximum power transfer,S-Parameters,Parameters for two-port system analysis Suitable for distributive e
6、lements Inputs and outputs expressed in powers Transmission coefficients Reflection coefficients,S-Parameters,a1,b1,b2,a2,S11,S12,S22,S21,S-Parameters,S11 input reflection coefficient with the output matched S21 forward transmission gain or loss S12 reverse transmission or isolation S22 output refle
7、ction coefficient with the input matched,S-Parameters,S,Z1,Z2,Vs1,Vs2,I1,V1,I2,V2,Stability Condition,Necessary condition where Stable iff where,A First LNA Example,Assume No flicker noise ro = infinity Cgd = 0 Reasonable for appropriate bandwidth Effective transconductance,Rs,Vs,Vs,Rs,4kTRs,Vgs,gmV
8、gs,4kTggm,io,Power Gain,Voltage input Current output,Noise Figure Calculation,Power ratio output Device noise + input-induced noise Input-induced noise,Unity Current Gain Frequency,0dB,fT,Ai,f,frequency,Small-Signal Model of MOSFET,Cgs Cgd rds Cdb Rg: Gate resistance ri: Channel charging resistance,
9、Vgs,gmVgs,Cgd,i1,i2,ri,Cgs,i1,i2,Cdb,rds,Rg,V1,V2,V1,V2,wT Calculation,Vgs,gmVgs,Cgd,i1,i2,ri,Cgs,Cdb,rds,Rg,V1,wT of NMOS and PMOS,0.25um CMOS Process*,2 Tajinder Manku, “Microwave CMOS - Device Physics and Design,” IEEE J. Solid-State Circuits, vol. 34, pp. 277 - 285, March 1999.,Set:,Solve for wT
10、,Noise Performance,Low frequency Rsgm g 1 gm 1/50 Rs = 50 ohm Power consuming CMOS technology gm/ID lower than other tech wT lower than other tech,Review of First Example,No impedance matching Capacitive input impedance Output not matched Power transfer S11=(1-sRCgs)/(1+sRCgs) S21=2Rgm/(1+sRCgs), R=
11、Rs=RL Power consumption High power for NF High power for S21,Impedance Matching for LNA,Resistive termination Series-shunt feedback Common-gate connection Inductor degeneration,Resistive Termination,Current-current power gain Noise figure,Rs,Vs,Is,Rs,4kT/Rs,Vgs,gmVgs,io,RI,RI,4kT/RI,4kTggm,Compariso
12、n with Previous Example,Previous example Resistive-termination,Introduced by input resistance,Signal attenuated,Summary - Resistive Termination,Noise performance Low-frequency approximation Input matched Rs = RI = R Broadband input match Attenuate signal Introduce noise due to RI NF 3 dB (best case)
13、,Series-Shunt Feedback,Broadband matching Could be noisy,Rs,Vs,Ra,RF,RL,Vgs,gmVgs,RF,iout,Ra,Cgs,Rs,Vs,RL,Common-Gate Structure,Rs,RL,Vs,Rs,4kTRs,Vgs,gmVgs,RL,4kTggm,Vs,Rs,4kTRs,Vgs,gmVgs,RL,4kTggm,gm,Input Impedance of CG Structure,Input impedance Yin=gm+sCgs Input-impedance matching Low frequency
14、approximation Direct without passive components 1/gm=Rs=50 ohm,Noise Performance of CG Structure,Signal attenuated,Power Transfer of CG Structure,Rs = RL = R = 50 ohm S11=0, S21=1 Low frequency,Summary CG Structure,Noise performance No extra resistive noise source Independent of power consumption Im
15、pedance matching Broadband input matching No passive components Power consumption gm=1/50 Power transfer Independent of power consumption,Inductor Degeneration Structure,Rs,Vs,Ls,Lg,Vgs,gmVgs,iout,Cgs,Rs,Vs,Lg,Ls,Zin,Vin,iin,Zin,Input Matching for ID Structure,Zin=Rs IMZin=0 REZin=Rs,Vgs,gmVgs,iout,Cgs,Rs,Vs,Lg,Ls,Zin,gmLs/Cgs,Effective Transconductance,Vgs,gmVgs,iout,Cgs,Rs,Vs,Lg,Ls,Zin,gmLs/Cgs,Noise Factor of ID Structure,Calculate NF at w0,= 0 w0,Input Quality Factor of
