Amplifier Feedback Topologies and Performance Analysis
Added on -2019-09-22
This article discusses different amplifier feedback topologies, including voltage amplifier/series-shunt feedback, current amplifier/shunt-sequence feedback, transconductance amp/series-series feedback, and transresistance amplifier/shunt-shunt feedback. It also covers the effect of feedback on amplifier performance, including input/output impedance, frequency response, distortion and noise reduction, and stability. The article includes a numerical problem and performance analysis of feedback on gain. Get solved assignments, essays, and dissertations on Desklib.
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AssignmentVoltage Amplifier/Series-shunt FeedbackSeries-shunt amps are designed to increase a source power indicator moreover supply aproductivity power indicator. The power amp is fundamentally a VCVS device. The inputimpedance of this source has to be elevated, as well as the productivity impedance should bevery short.As at the input side, the connection is sequence and at the output side, the connection isparallel, therefore, this kind of amplifier response topology is called because sequence-shuntviews.Current Amplifier/Shunt-Sequence FeedbackHere, the output physical quantity is current; therefore the view network must be able tosample the current. The view indicator must be in the type of in order that it can getcombined in parallel by the input supply current. Therefore the amplifier response topologywhich suits our requirement is the current-merging current-sampling topology. Since the linknext to the input is shunt as well as the connection next to the productivity is sequence,therefore the feedback topology is moreover recognized as shunt-sequence response. Thistopology stabilizes the current increase and also provides a low key resistance furthermore ahigh productivity resistance. These are two attractive properties in support of a current amp.
Transconductance Amp/Series-Series FeedbackThis amplifier is known as trans-conductance amplifier since the gain of the amplifier givesthe ratio of current to voltage. Inside this amp, voltage is the input indicator and current is theproductivity signal. Since the series link exists next to both the input furthermore theproductivity side, the feedback topology is also recognized the same as series-seriesfeedback.Transresistance Amplifier/Shunt-Shunt FeedbackIn trans-resistance amps the input indicator is current as well as the productivity signal ispower. It pursues that the suitable response topology is of the current-blending power-sampling form. The existence of the equivalent (or force) link by the side of equally the inputas well as the productivity creates this feedback topology recognized like shunt-shuntresponse too.
Effect of Response on Amplifier PerformanceCharacteristicPower SequenceCurrent SequenceCurrent ShuntVoltage ShuntFeedback SignalPowerPowerCurrentCurrentSampled SignalPowerCurrentCurrentPowerFeedback Gain(B)Feedback voltage/output voltageFeedback voltage/output currentFeedback Current/Input CurrentFeedback Current/Output VoltageOpen Loop GainAv= Vo/ViGm=Io/ViAi=Io/IiRm=Vo/IiD1+BAv1+BGm1+BAi1+BRmAfAv/DGm/DAi/DRm/DRifRiDRiDRi/DRi/DRofRo/DRoDRoDRo/DNumerical ProblemXo = A XiXf = B XoXi = Xs – XfXo = A(Xs - Xf)Xo = A Xs – A XfX o = A Xs – AB XoXo (1 + AB) = A XsXo/Xs = A/(1 + AB)To convert the decibels into magnitude, we use the formulagain in dB = 20 log (gain in numerals)Putting the values99 = 20 log (A)A = 10 (99/20)A = 104.5
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