ECE 2006Differential AmplifierCommon Mode RejectionOperational AmplifierOp Amp CharacteristicsEquivalent Circuit ModelIdeal Op AmpFeedbackAnalysis of Ideal Op Amp CircuitsBasic Op Amp CircuitsInverting AmplifierNon-Inverting AmplifierSumming AmplifierDifference AmplifierAnalysis of the Voltage FollowerReferencesECE 2006Chapter 5:Operational AmplifiersDifferential Amplifier•Not Practical Prior to IC Fabrication•2 Inputs, Output is Av*(V1 - V2)Common Mode Rejection•Differential Amps won’t Amplify Signals that are Common to both InputsOperational Amplifier•Three Stages: –Differential Amplifier (Input Stage)–Voltage Amplifier (High Gain)–Output Stage (low output impedance)Op Amp Characteristics•High Input Impedance ( 1 M-Ohm)•Low Output Impedance (100 Ohms)•High Voltage Gain (100,000)•2 Differential Inputs–Inverting Input (V-)–Non-Inverting Input (V+)Equivalent Circuit Model•Differential Input Voltage determines Output VoltageIdeal Op Amp•Input Impedance is Infinite (No input Current)•Voltage Gain is Infinite•Inverting and Non-inverting inputs at equal potentialFeedback•Open Loop Voltage Gain is so High that External Feedback is always used•Output Signal is Fed Back to an Input TerminalAnalysis of Ideal Op Amp Circuits•Set V- = V+ and I- = I+ = 0•Write Nodal Equation(s)Basic Op Amp Circuits•Voltage Follower: Impedance Matching or Isolation•Unity Gain: Vout = VinInverting Amplifier•Vout = -(R2/R1)*VinNon-Inverting Amplifier•Vout = Vin*(R1+R2)/R1Summing Amplifier•Vout = -(V1*Rf/R1 + V2*Rf/R2 + V3*Rf/R3)Difference Amplifier•Vout = (V2-V1)*R2/R1Analysis of the Voltage Follower•Provides “Current Isolation” – No Power Drawn from Input CircuitReferences•Heathkit, Electronic Circuits, EB-6104A, 2002•Alexander, Fundamentals of Circuit Analysis – 2nd Edition, McGraw-Hill,
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