Why my op-amp differentiator output waveform not perfect

Discussion in 'Analog & Mixed-Signal Design' started by Harvey Wang, Mar 16, 2018.

  1. Harvey Wang

    Thread Starter New Member

    Mar 16, 2018
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    0
    Hi all,
    I created a op-amp differentiator by myself using LM741 and capacitor with100nf resistor with 10k ohms. However, when I input Ramp signal, my output waveform is like this(graph below). I don’t know why, how can I fix it? 6183F38A-06EF-4B16-9708-251FEE300BF9.png
     
  2. ericgibbs

    Moderator

    Jan 29, 2010
    7,530
    1,517
    hi Harvey,
    Welcome to AAC.
    Please post a circuit diagram of your project.
    E
     
  3. crutschow

    Expert

    Mar 14, 2008
    21,713
    6,262
    Try 2.5nF across the 10kΩ feedback resistor.
     
  4. MrChips

    Moderator

    Oct 2, 2009
    18,339
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    Are we to assume that trace C1 is the input signal and trace C2 is the output of your differentiator?

    What is the make and model of your oscilloscope?
    What are you using as oscilloscope probes?
     
  5. Audioguru

    Expert

    Dec 20, 2007
    10,963
    1,253
    An LM741 opamp was designed 50 years ago! Its performance is terrible compared to modern opamps.
     
  6. DickCappels

    Moderator

    Aug 21, 2008
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    1,672
    Yep, the LM741 is probably having trouble slewing at the end of each slope.

    Also notice that your triangle waveform is nonlinear for the first
    approximately 50 us of each slope.
     
  7. crutschow

    Expert

    Mar 14, 2008
    21,713
    6,262
    Simulation shows that about 250Ω in series with the input capacitor slows down the slew rate so there's no overshoot or ringing (if it's a standard op amp RC differentiator), even with the lowly old 741.
     
  8. danadak

    Distinguished Member

    Mar 10, 2018
    2,773
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