This op amp does not have gain?

  • Thread starter EENSEEY
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  • #1
EENSEEY
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TL;DR Summary
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
 

Answers and Replies

  • #2
berkeman
Mentor
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Welcome to PF. :smile:

It looks fine to me...

1628516050512.png

https://www.electronics-tutorials.ws/opamp/opamp_7.html
 
  • #3
EENSEEY
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Thanks!
 
  • #4
LvW
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251
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?
 
  • #5
DaveE
Science Advisor
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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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