This op amp does not have gain?

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SUMMARY

The discussion centers on the behavior of operational amplifiers (op amps) in inverting configurations, specifically addressing gain in both DC and AC circuits. It is established that a coupling capacitor blocks DC and does not provide a reference for gain, while AC gain requires a capacitor in the feedback loop. The circuit discussed, a differentiator, operates under ideal conditions only and can become unstable in real-world applications. Feedback stability, Bode plots, and bandwidth limitations are critical concepts for understanding op amp performance.

PREREQUISITES
  • Understanding of operational amplifier configurations
  • Knowledge of feedback stability in electronic circuits
  • Familiarity with Bode plots and frequency response
  • Basic concepts of capacitors, inductors, and resistors in AC circuits
NEXT STEPS
  • Study feedback mechanisms in simple amplifiers
  • Learn about the frequency-dependent behavior of capacitors and inductors
  • Explore Bode plots for analyzing system stability
  • Investigate bandwidth limitations of real-world amplifiers
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Electronics students, circuit designers, and engineers interested in operational amplifier behavior and feedback stability in electronic circuits.

EENSEEY
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this op amp doe snot have again in AC or DC
Had this as a question from a class mate. This op amp should not have any gain in the DC or AC circuit. The coupling cap blocks DC and has no reference to get gain, while the AC needs a cap in the feedback loop to get gain. Is that correct? Oh, this is supposed to be in the inverting configuration.

1628515130391.png
 
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Welcome to PF. :smile:

It looks fine to me...

1628516050512.png

https://www.electronics-tutorials.ws/opamp/opamp_7.html
 
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Thanks!
 
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EENSEEY, you should realize that the shown circuit (differentiator) will work under ideal conditions only (ideal opamp with a gain that is not frequency-dependent).
Under real conditions the circuit will be unstable.
Question: Why do you think that a cap is required in the feedback path to get gain?
 
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Yes, what @LvW said. This is actually a very difficult circuit to make work without oscillation. You'll learn more about that later when you've studied more about feedback stability, bode plots, and and the bandwidth limitations of real world amplifiers.

A cap in the feedback path will reduce the overall AC gain, not increase it. More feedback makes less forward gain.

Your next step should be to study about feedback in simple amplifiers, and the frequency dependent behavior of the basic components: inductors, capacitors and resistors.
 

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