RF Power Amplifiers

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The World Leader in High-Performance Signal Processing SolutionsRF IFRF Power AmplifiersMay 7, 20032RF IFOutline PA IntroductionzPower transfer characteristicszIntrinsic PA metricszLinear and Non-linear amplifierszPA Architectures Single-Stage Linear PAzLoad-line theoryzTransistors size zInput and Output MatchingzSo why is this so hard? High- efficiency PAszClass A, AB, B and C amplifiers3RF IFOutline (cont.) Real-World Design ExamplezSelecting architecture, number of stageszDesigning stageszTuning: inter-stage match and output System specificationszRuggedness: load mis-match and VSWRzLinearity: spectral mask (ACPR), switching transientszNoise in receive band Power Control4RF IFPA Transfer characteristicsDefining linearity:G01Pin(dBm)Pout(dBm)Pout= Pin+ Glinearnon-linear (actual)5RF IFPA Transfer characteristicsDefining linearity:Gain (dB)Pin(dBm)Pout(dBm)G-1P1dBPMAX6RF IF

High-Efficiency PAs If all harmonics filtered out, then voltage output at load is a pure sinusoid, despite discontinuous conduction V ωt OUT π 2π 3π I C π 2π 3πωt I MAX Energy stored in reactive elements delivers current to the load during transistor off-portion of cycle

  Efficiency, Energy