Open loop gain Op-amp?

Discussion in 'General Electronics Chat' started by dtvonly, Feb 19, 2013.

  1. dtvonly

    Thread Starter Member

    Dec 14, 2012
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    Hi. what is the function of the attached circuit? I would think that the op-amp is configured as a open-loop gain amplifier. Therefore, the output will always be Vcc or +15V (ideally). Is this correct? Thank you.
     
  2. crutschow

    Expert

    Mar 14, 2008
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    Yes, the output capacitor means there is no DC feedback and thus the op amp will go to the positive rail for any positive input.
     
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  3. Jaguarjoe

    Active Member

    Apr 7, 2010
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    Isn't that an integrator of sorts?
     
  4. dtvonly

    Thread Starter Member

    Dec 14, 2012
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    at first glance, it may appeared as a integerator configuration. If it is an integrator, then I have not seen it in this form before. In fact, I had searched the web but nothing (in this form) came up. So why use it at all if its output will just be from rail-to-rail no matter what? This is a real circuit that a hardware engineer at my company is using in his power supply design. I am a firmware/software developer who used to be in hardware. I guess I am just getting rusty at H/W now.
     
  5. JMac3108

    Active Member

    Aug 16, 2010
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    The circuit has infinite DC gain but the gain rolls off at higher frequencies as the capacitor impedance is reduced. At a high enough frequency the gain is 1+ (1k/10k) = 1.1.

    Normally you would have a resistor in parallel with the cap to limit the DC gain.
     
  6. crutschow

    Expert

    Mar 14, 2008
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    That circuit would work only if it is part of a feedback loop with DC feedback.
     
  7. bountyhunter

    Well-Known Member

    Sep 7, 2009
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    Looks like a comparator with some AC rolloff?
     
  8. crutschow

    Expert

    Mar 14, 2008
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    What would be the purpose of a comparator with AC rolloff? :confused:
     
  9. t06afre

    AAC Fanatic!

    May 11, 2009
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    Academic exercise I think
    :rolleyes:
     
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