I'm trying to understand op-amp operation, starting with the buffer circuit. I have simulated the voltage follower using an LM324 in Multisim Live. I was trying to simulate output saturation by changing the magnitude of the input voltage to the buffer to drive the op-amp beyond the power supply limits. The image included at the end of the post is my Multisim Live schematic and simulation results.

2 issues confuse me:

  1. How do I determine the min/max output voltages from the datasheet? The info given is for single supply operation, however the op-amp is described as dual supply up to +-16V. Not sure how to convert the VOH and VOL specs from single supply to dual supply. The VOH spec is also state for V+ =30V, so not sure how to convert to +5V. enter image description here

  2. The simulation results show the op-amp in both positive and negative saturation. However the negative saturation is below VEE for the simulation. Regardless of how close the output can get to the rails, my simulation shows it clipping below the negative rail. I can't make heads or tails of this.

enter image description here

  • 1
    \$\begingroup\$ Negative saturation being below V_EE sounds to me like it's more a bug in the simulation than anything else. \$\endgroup\$ – Hearth Mar 25 '20 at 15:33
  • \$\begingroup\$ A weakness of the model. Just accept that it won't go below the negative rail. You might try loading it up with (say) 1 kohm to fight the 50 uA constant current sink inside the 324. The modelers probably just implemented it as a 50 uA constant current and neglected to worry about implications. \$\endgroup\$ – Andy aka Mar 25 '20 at 15:47

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