linera_lna

linera_lna - A New LinearityEnhancingTechniquefor...

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Unformatted text preview: A New LinearityEnhancingTechniquefor LowNoiseAmplifiers AmitGopalM. Purohit DA-IICT Gandhinagar,Gujarat,India amit purohitadaiict.ac.in Abstract Inthispaper atechnique isproposed toenhance the linearity of low noise amplifier using nonlinearity of other components. Thistechniqueincreases11P3oflownoiseamplifier without large increase in overall noise figure of LNA. This technique can be very useful for 802.11 b/g and Bluetooth applications where high linearity with low noise figure is required.Linearityimprovementbyuseofnonlinearcomponents isthe basic idea for IIP3 improvement ofthis LNA. Currents produced by two amplifiers having different linearity characteristicsarefedtocurrentsubtractorwhichgivescurrent having good linearity characteristics but having a lower gain. Simulations based on layoutofproposed architectureshow that thisarchitectureincreasesIIP3upto10+dBm andthecircuitis suitableforlow noiseapplications. Amplifier achieves againof 10.5dB, noisefigureof1.5dB and dissipates 14.5 mwatts power from1.8voltssupply. I. INTRODUCTION The development of CMOS technology in to deep sub micronenablestheuseofsuchtechnologyforimplementation forGHz RF circuits.Personalcommunicationneedsalowcost and low noise RF transceiver forcellularapplicationsusing CMOS technology. Low Noise amplifierisone ofthebasic buildingblocksinanyreceiversystem.The LNA determines theoverallsystem'snoiseperformance,asitisfirstblockafter antenna.LNA mustamplifytheinputsignalwithlowestnoise possiblebecause itdecides the whole device's performance undernoisysignal.Inordertohavehighreceiversensitivitythe LNA isrequiredtohavenotonlylownoisefigurebutalsohigh gainandlowinputVSWR Normally,LNA designinvolvesthetradeoffbetweennoise figure,gain,linearityandpower consumption.Consequently, thegoalofLNA designistomeet systemrequirementswith minimumnoisefigureandhighestpossiblelinearity.TheLNA designoptimizationtechniqueproposedin[10]canbeapplied forpowerconstrainedsimultaneouslynoiseandinputmatching [2]. This paper attempts to propose a linearity enhancing techniquetosimultaneouslymatchhighlinearityandlownoise figurerequirements.The designisbaseduponthethirdorder intermodulationproduct(IM3)andoutputcurrentequationsof aMOSFET whenitissubjectedtoanacinput signal.Byusing theseexpressions,thedesignprinciplesandadvantages Dr.SanjeevGupta DA-IICT Gandhinagar,Gujarat,India Sanjeev_gupta adaiict.ac.in output Figure1.CircuitdiagramofdesignedLNA forthementionedLNA techniqueareexplained.Inaddition,in this paper the overall noise figure as well as total power reductionisachievedbyusinganexternalcapacitorinbetween gateandsourceterminalsofcommonsourceamplifier. Although therearealotofways toincreaselinearityof amplifierbuteach andeverymethod has itsown limitation....
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linera_lna - A New LinearityEnhancingTechniquefor...

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