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# Understanding Voltage, Current, Transconductance and Transresistance Amplifiers

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This article explains the characteristics and feedback loop design of voltage, current, transconductance and transresistance amplifiers. It also discusses the effect of feedback on amplifier performance and how it improves sensitivity and bandwidth. The article includes a numerical problem and a performance analysis of feedback on gain. Subject: Electrical Engineering, Course Code: EE101, College/University: Desklib
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AssignmentVoltage AmplifiersCharacteristics of Voltage amplifiersoThe input and output signal in the circuit are both voltage signal.oThis is a VCVS device which is Voltage-controlled voltage source.oThis circuit is characterised by its input impedance that is high and acomparatively lower output impedanceAmplification Feedback topologyoIn this, the sampling is of Voltage and mixing is of series (series-shunt)topologyThe output voltage signal is used as the source for the feedbacknetwork and feedback signal xf is fed into the input through a seriesconnection Here the word “Series” is used to define the feedback signal collectedfrom the output signal sample and sent to the input and the feedbackcircuit at output is represented by the term “shunt” which meansparallel.oCharacteristics:This circuit stabilizes the voltage gain.The resistance in series at the input gives higher resistance in input.The parallel resistance at the output gives lower resistance at output.Current AmplifierCharacteristics of Current Amplifiers:oThe input and output signals are both current.oIt is a CCCS source which stands for Current-controlled current sourceoThis amplifier has low input impedanceoThis amplifier has high input impedanceAmplifier Feedback loop designoCurrent-sampling shunt-series designThe feedback loop takes sample of the output current and generates thefeedback current that can be mixed with the input signal in parallel.The term “Shunt” is related to the input connection and the term“series” is related to the output connection.Characteristics:oThis circuit stabilizes the current gain.
oIn this current amplifier circuit, the input port of the amplifier is characterisedby low input impedance and the high output impedance.Transconductance AmplifierCharacteristics of a trans-conductance amplifier:oThe Input signal in this amplifier is characterised as voltage signal and theoutput signal is characterised as current signal.oThis is a VCCS device which stands for Voltage-controlled current source.oThis amplifier provides high input impedance.oThis amplifier provides high impedance in its output.Feedback designoThis is series-series design which means Current-sampling series-mixing.The feedback network takes sample of the output and generates thefeedback voltage signal xf that is fed into the input signal voltagethrough series connection.There the term “Series” is related to the resistance connected in theinput and outputCharacteristics:oThis amplifier stabilizes the trans-conductance gainoThe trans-conductance amplifier gives high input resistance and offers highoutput resistance for the amplifier.
Transresistance AmplifierCharacteristics of trans-resistance amplifier:oThe input of a trans-resistance amplifier is current and output signal ischaracterised as a voltage signal.oIt is a CCVS device which stands for Current-controlled voltage source.oThis amplifier has low ohmage at both input and output Feedback loop designoVoltage-sampling parallel-parallel designThe feedback mechanism situated at output terminal takes sample ofoutput voltage and generates feedback current xf that is sent to theinput through parallelThe term “Shunt” is refers to the parallel connected resistance at boththe input and output connection.Characteristics:oThis amplifier stabilizes the trans-resistance gain.oThe input of the trans-resistance amplifier provides low input resistance andthe output provides low output resistance.Effect of Feedback on Amplifier PerformanceCharacteristicVoltage SeriesCurrent SeriesCurrent ShuntVoltage ShuntFeedback SignalVoltageVoltageCurrentCurrentSampled SignalVoltageCurrentCurrentVoltageFeedback 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 Problem

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