6.2.2 Inverting Amplifiers

Chapter 6.2.2 Inverting Amplifiers

Physics Lecture Notes – Phys 395 Electronics Book
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Physics Lecture Notes – Phys 395 Electronics Book

  • CHAPTER 6. OPERATIONAL AMPLIFIERS108The amplifier gives a unit closed-loop gain, G(jω) = 1, and does not change the sign of theinput signal (no phase change).This configuration is often used to buffer the input to an amplifier since the input resis-tance is high, there is unit gain and no inversion. The buffer amplifier is also used to isolatea signal source from a load.Often a feedback resistor is used as shown in figure 6.3.VoutI=0VinRFRIFigure 6.3: Non-inverting amplifier with feedback.For this circuitV+ = V− ⇒ Vin =RIRI + RFVout.(6.6)The gain isVoutVin=RI + RFRI=1 +RFRIand(6.7)G(jω)=1 +RFRI.(6.8)(6.9)6.2.2Inverting AmplifiersAn inverting amplifier is shown in figure 6.4. Analysis of the circuit givesVin− V−RI=V− − VoutRF.(6.10)Since V+ = V− =0 (V− is at virtual ground),VinRI=−VoutRF.(6.11)The gain is