SourceForge has been redesigned. Learn more.
Close

Opamp AC simulation

Help
noachr
2007-11-27
2014-02-28
  • noachr

    noachr - 2007-11-27

    I am trying to test the frequency response of a simple opamp circuit with an ac simulation. However, when I run it I get:

    checker error, a .DC action is required for this circuit definition (accounted 1 non-linearities)

    Any help would be appreciated.

    Here is the schematic:

    <Qucs Schematic 0.0.12>
    <Properties>
      <View=0,0,944,1094,1,0,120>
      <Grid=10,10,1>
      <DataSet=opamp.dat>
      <DataDisplay=opamp.dpl>
      <OpenDisplay=1>
      <showFrame=0>
      <FrameText0=Title>
      <FrameText1=Drawn By:>
      <FrameText2=Date:>
      <FrameText3=Revision:>
    </Properties>
    <Symbol>
    </Symbol>
    <Components>
      <GND * 1 460 370 0 0 0 3>
      <R R2 1 380 570 -26 15 0 0 "1 kOhm" 1 "26.85" 0 "0.0" 0 "0.0" 0 "26.85" 0 "US" 0>
      <GND * 1 290 570 0 0 0 3>
      <Vac V3 1 320 570 -26 18 0 0 "3 V" 1 "1 kHz" 0 "0" 0 "0" 0>
      <.AC AC1 1 140 770 0 46 0 0 "lin" 1 "0 Hz" 1 "50 kHz" 1 "1000" 1 "no" 0>
      <OpAmp OP2 1 490 390 -26 42 0 0 "1e6" 1 "15 V" 0>
      <R R1 1 520 570 -26 15 0 0 "5 kOhm" 1 "26.85" 0 "0.0" 0 "0.0" 0 "26.85" 0 "US" 0>
      <C C1 1 520 660 -26 17 0 0 ".1 uF" 1 "" 0 "neutral" 0>
    </Components>
    <Wires>
      <410 570 460 570 "" 0 0 0 "">
      <590 390 590 570 "" 0 0 0 "">
      <530 390 590 390 "" 0 0 0 "">
      <460 410 460 570 "" 0 0 0 "">
      <550 570 590 570 "" 0 0 0 "">
      <460 570 490 570 "" 0 0 0 "">
      <590 570 590 660 "" 0 0 0 "">
      <550 660 590 660 "" 0 0 0 "">
      <460 570 460 660 "" 0 0 0 "">
      <460 660 490 660 "" 0 0 0 "">
      <350 570 350 570 "Vin" 370 520 0 "">
      <590 390 590 390 "Vout" 620 360 0 "">
    </Wires>
    <Diagrams>
    </Diagrams>
    <Paintings>
    </Paintings>

     
    • Stefan Jahn

      Stefan Jahn - 2007-12-01

      Hi there!

      Put an DC simulation into the schematic.

      Hope this helps, Stefan.

       
  • BrendaEM

    BrendaEM - 2014-02-28

    I also have this error in my circuit. I am disappointed because Qucs looks like a great and intuitive program.

    I was hoping to simulate an "Mu-Amp" FET tube-emulator, for which I want to test AC.

    I tried adding a DC simulation; the output I have looks only like flatlined DC. Something seems broken.

    Any help would be...helpful. Thanks : )

    My Error: checker error, a .DC action is required for this circuit definition (accounted 2 non-linearities)

    My System: Windows 7/64Bit

    My Qucs 0.0.17

    My Schematic version without adding DC simulation:

    <Qucs Schematic 0.0.17>
    <Properties>
      <View=0,120,1102,960,1.15866,0,13>
      <Grid=10,10,1>
      <DataSet=Amp Schematic 001.dat>
      <DataDisplay=Amp Schematic 001.dpl>
      <OpenDisplay=1>
      <Script=Amp Schematic 001.m>
      <RunScript=0>
      <showFrame=0>
      <FrameText0=Title>
      <FrameText1=Drawn By:>
      <FrameText2=Date:>
      <FrameText3=Revision:>
    </Properties>
    <Symbol>
    </Symbol>
    <Components>
      <GND * 1 640 700 0 0 0 0>
      <JFET J2N3684_1 1 570 370 9 -9 0 0 "nfet" 0 "-3.18" 0 "348.1u" 0 "11.67m" 0 "1" 0 "1" 0 "114.5f" 0 "1" 0 "1.091p" 0 "2" 0 "2.083p" 0 "2p" 0 "0.5" 0 "0.5" 0 "0.2271" 0 "1.259e-018" 0 "1" 0 "1" 0 "26.85" 0 "3" 0 "0" 0 "-0.5" 0 "26.85" 0 "1" 0>
      <GND * 1 480 810 0 0 0 0>
      <JFET J2N3684_2 1 570 660 19 -9 0 0 "nfet" 0 "-3.18" 0 "348.1u" 0 "11.67m" 0 "1" 0 "1" 0 "114.5f" 0 "1" 0 "1.091p" 0 "2" 0 "2.083p" 0 "2p" 0 "0.5" 0 "0.5" 0 "0.2271" 0 "1.259e-018" 0 "1" 0 "1" 0 "26.85" 0 "3" 0 "0" 0 "-0.5" 0 "26.85" 0 "1" 0>
      <C C1 1 470 500 17 -26 0 1 ".1 uF" 1 "" 0 "neutral" 0>
      <R R4 1 570 570 15 -26 0 1 "1k" 1 "26.85" 0 "0.0" 0 "0.0" 0 "26.85" 0 "US" 0>
      <R R5 1 480 750 15 -26 0 1 "10M" 1 "26.85" 0 "0.0" 0 "0.0" 0 "26.85" 0 "US" 0>
      <R R3 1 400 370 -26 15 0 0 "4.7M" 1 "26.85" 0 "0.0" 0 "0.0" 0 "26.85" 0 "US" 0>
      <R R2 1 270 420 15 -26 0 1 "10k" 1 "26.85" 0 "0.0" 0 "0.0" 0 "26.85" 0 "US" 0>
      <R R1 1 270 320 15 -26 0 1 "10k" 1 "26.85" 0 "0.0" 0 "0.0" 0 "26.85" 0 "US" 0>
      <GND * 1 170 460 0 0 0 0>
      <C C2 1 170 430 17 -26 0 1 ".1 uF" 1 "" 0 "neutral" 0>
      <GND * 1 270 460 0 0 0 0>
      <GND * 1 640 330 0 0 0 0>
      <GND * 1 380 720 0 0 0 0>
      <Vac V2 1 380 690 18 -26 0 1 "1 V" 1 "1 kHz" 0 "0" 0 "0" 0>
      <Vdc V3 1 640 300 18 -26 0 1 "9 V" 1>
      <.AC AC1 1 70 780 0 46 0 0 "lin" 1 "20 Hz" 1 "20000 Hz" 1 "1000" 1 "no" 1>
    </Components>
    <Wires>
      <480 660 480 720 "" 0 0 0 "">
      <480 660 540 660 "" 0 0 0 "">
      <570 690 570 700 "" 0 0 0 "">
      <570 700 640 700 "" 0 0 0 "">
      <570 600 570 630 "" 0 0 0 "">
      <570 400 570 460 "" 0 0 0 "">
      <480 780 480 810 "" 0 0 0 "">
      <470 370 540 370 "" 0 0 0 "">
      <470 370 470 470 "" 0 0 0 "">
      <470 600 570 600 "" 0 0 0 "">
      <470 530 470 600 "" 0 0 0 "">
      <570 460 570 540 "" 0 0 0 "">
      <430 370 470 370 "" 0 0 0 "">
      <270 260 570 260 "" 0 0 0 "">
      <270 370 370 370 "" 0 0 0 "">
      <270 350 270 370 "" 0 0 0 "">
      <270 370 270 390 "" 0 0 0 "">
      <270 260 270 290 "" 0 0 0 "">
      <170 370 270 370 "" 0 0 0 "">
      <170 370 170 400 "" 0 0 0 "">
      <380 660 480 660 "" 0 0 0 "">
      <640 260 640 270 "" 0 0 0 "">
      <270 450 270 460 "" 0 0 0 "">
      <570 460 760 460 "" 0 0 0 "">
      <570 260 640 260 "" 0 0 0 "">
      <570 260 570 340 "" 0 0 0 "">
      <380 660 380 660 "Vin" 330 640 0 "">
      <760 460 760 460 "Vout" 790 430 0 "">
    </Wires>
    <Diagrams>
    </Diagrams>
    <Paintings>
    </Paintings>
    
     
    Last edit: BrendaEM 2014-02-28
  • Romano Giannetti

    I have a similar problem --- simply using the (BJT based) 741 model in the library, doing a buffer with it, and trying a dc polarization will fail.
    It seems that complex nonlinearities make QUCS barf very easily.
    Anyone here that can help?

     
  • BrendaEM

    BrendaEM - 2014-02-28

    Romano, thanks for chiming in.

    I posted a bug report here: https://sourceforge.net/p/qucs/bugs/146/

    If you want to add to that, it may help. Thank you.

     
    Last edit: BrendaEM 2014-02-28
  • Guilherme

    Guilherme - 2014-02-28

    Hum...
    For the first issue raised in 2007 by noachr.
    If you add a DC simulation and avoid the 0Hz in the frequency sweep... I think it works. I did not calculate the 3dB pole... but the low pass behavior is there. (attached schematic)

    I am not familiar with the "Mu-Amp", what is the expected behavior? From the DC analysis are the JFET properbly biased? Maybe the 2N3684 parameters are wrong??

     

Log in to post a comment.