I want to use this circuit to generate a triangle wave from 100mv to 10v and an inverted wave from -100mv to -10v on triangle_inv. For my split rail supply, i'm using the VG1 circuit from this page virtual ground circuit

wave generator

It works correctly generating the positive wave, however the wave on triangle_inv is centered on 0v. It's inverted like it's supposed to be, but where's the offset coming from?

scope trace

  • 1
    \$\begingroup\$ Try connecting pin 5 to ground through a 5k resistor instead of directly. If that mostly solves the problem, then the answer to your question is "offset current". \$\endgroup\$
    – The Photon
    Feb 24, 2020 at 2:22
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    \$\begingroup\$ What does the green '~' symbol mean on the scope display after "CH2"? \$\endgroup\$ Feb 24, 2020 at 2:25
  • \$\begingroup\$ Research "op amp nonidealities and limitations," and in particular the topics of input offset voltage, input offset current, and input bias current. IMO, Mateo Aboy, on his YouTube channel, does a pretty good job of introducing these three effects: youtu.be/JiMhJJLplkQ and youtu.be/1tUaDghBmuc. Also, the LM324 is not a precision op amp, so you can and should expect a slight DC offset at the output. \$\endgroup\$ Feb 24, 2020 at 5:01
  • \$\begingroup\$ @Bruce Abbott nice catch \$\endgroup\$
    – user156429
    Feb 24, 2020 at 21:48
  • \$\begingroup\$ @Bruce Abbot. Ac coupling facepalm . Turns out the waveform was correct, but my scope got rid of the dc offset because i had it set up wrong \$\endgroup\$ Feb 25, 2020 at 3:14

1 Answer 1


I had channel 2 on AC coupling. My circuit was actually outputting the right waveform but my scope was lying to me. Facepalm


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