enter image description here

The simulation works OK when I run with ideal op-amp but the problem comes whenever I change the op-amp to a real one (LMH6642MF) and that results in a converge error and a warning. I have tried to find the problem by changing the power supply to ±15 V for the op-amp.

The above figure is the circuit.

Please help me find the problem. I really have to make it work because I have a deadline in my uni in 4 days. :(


edit: Is it normal for the regulator to draw a lot of currents (app.7A) when there is no load at the output? see image down for the current draw enter image description here

  • \$\begingroup\$ if u need the simulation I can send it through mail or other ways just ask! \$\endgroup\$ – newbie123 May 7 '20 at 5:00
  • 2
    \$\begingroup\$ It's probable that your generic Spice opamp has 1 pole behavior and is kind of slow. Your TI device is high speed with super high output current compliance (I'm impressed.) It's likely that the speed of the device model is causing the convergence troubles. Try putting a few pF (picoFarads) across your feedback resistors and see if that helps the convergence. You could also play with Gmin, I suppose. \$\endgroup\$ – jonk May 7 '20 at 5:13
  • \$\begingroup\$ thanks for the comment I will try it now \$\endgroup\$ – newbie123 May 8 '20 at 15:38
  • \$\begingroup\$ The problem still occurs... I think it has something to do with the current being drawn too much, even though I haven't connected any load to the lm2679. Is it normal that it draws 7amps without any load? \$\endgroup\$ – newbie123 May 8 '20 at 16:49

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