6.3 Analysis Using Finite Open-Loop Gain

Chapter 6.3 Analysis Using Finite Open-Loop Gain

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

  • CHAPTER 6. OPERATIONAL AMPLIFIERS122Figure 6.26: Straight-line approximation to|G| for amplifier c).d)V2− V−ZC + R2=V− − 0R1(6.62)V2− V11/jωC + R2=V1R1(6.63)ThereforeV2 =1/jωC + R2R1V1 + V1(6.64)G(jω)=1 +R2R1+1jωR1C(6.65)ω→ 0⇒ G =1/(jωR1C);|G| =1/(R1C)ω−1.ω→∞⇒ G =1 + R2/R1;|G| =1 + R2/R1.1R1CωC=1 +R2R1 → ωC =1CR1+CR2.6.3Analysis Using Finite Open-Loop GainThe infinite gain approximation is very useful but a more complete description is requiredif we are to understand the limitations of the op-amp. Real op-amps have a large but finite