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[help] understanding Op-Amp frequency characteristics

  1. Nov 23, 2015 #1
    Hi

    I need help understanding the frequency characteristics of operational amplifiers. I do not understand why the output of an Op-Amp behaves much differently when the frequency of the input is increased.

    For example during the lab when the input to an inverting Op-Amp circuit was a sine wave.
    At 1kHz it behaved as normal.
    At 50kHz the output was not inverting anymore but triangular-like instead, as shown in the picture. Could anyone explain why the output behaves like this? inverter50khz.JPG
     
  2. jcsd
  3. Nov 23, 2015 #2

    Svein

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    Science Advisor

    This is called slew rate limiting and is part of the OpAmp specification.
     
  4. Nov 23, 2015 #3
    Ok thanks for your answer Svein. I have never heard of "slew rate" but I will look into it :D
     
  5. Nov 23, 2015 #4

    LvW

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    Slew rate is a large-signal parameter that describes the ability of the output voltage to follow the input voltage - indpendent on the gain (which is a small-signal parameter).
    That means: When you drastically decrease the input (and, therefore also) the ouput voltage you should see that the triangle waveform returns to a sinusoidal form (when the peak amplitude is small eneough)
     
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