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I've simulatated this circuit with Multisim and obtained an output that seems correct:

enter image description here

I built the same circuit on a breadboard and analyzed it with an oscilloscope:

enter image description here

The output of the real oscilloscope is quite different:

enter image description here

I cant't view the right side of the simulated signal (when it rises from - 5V to zero.)

What is wrong?

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    \$\begingroup\$ The simulation shows the button being pressed then released. The scope trace only shows the button being pressed. \$\endgroup\$
    – jayben
    Mar 30, 2022 at 11:34

2 Answers 2

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  1. Set the oscilloscope to a longer sweep time - the Multisim oscilloscope is set to 10 milliseconds per division while the real scope is set to (I think) 4 milliseconds per division.
  2. Press and release the button. Do not hold it down. The time period between the two peaks is the time you held the button down. If you hold the button too long then the oscilloscope can't get the press and release on screen at the same time.

You may need to set the oscilloscope to something like 50 or 100 milliseconds per division to get both peaks visible at once. It depends on how quickly you can press and release the button.

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  • \$\begingroup\$ Works fine with 20 ms. Thanks \$\endgroup\$
    – M4Biz
    Mar 30, 2022 at 13:46
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[How do I] view the right side of the simulated signal (when it rises from - 5V to zero.)

Any one of these should do it:

  1. Press and release the button faster, so the waveform is visible in the time displayed (horizontal axis.)
  2. Reduce (slow) the horizontal axis to show a longer duration of signal.
  3. Change the the channel trigger method from Rising Edge to Falling Edge.
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