RF Power Amplifiers - MIT OpenCourseWare

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:G01 Pin(dBm)Pout(dBm)Pout= Pin+ Glinearnon-linear (actual)5RF IFPA Transfer characteristicsDefining linearity:Gain (dB)Pin(dBm)Pout(dBm)G-1P1dBPMAX6RF IFPA Introduction: Intrinsic PA Metrics P1dB: Output Power at which linear gain has compressed by 1dB (measure of linear Power handling) PMAX: Maximum output Power (saturated Power ) Gain: Generally taken to mean transducer gain PAE: Power -added Effici

8 RF IF Linear and Non-linear PAs “Non-linear PA” generally refers to a PA designed to operate with constant P IN, output power varies by changing gain P OUT (dBm) P IN (dBm) Designed to operate here: NOT fixed gain! P OUT adjusted through bias control Operation in saturated mode leads to high peak efficiencies > 50%; “backed-off” efficiencies drop quickly

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