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LMV796 and LMV797 Incorrect SPICE Model

Ashiful Khurashi
Prodigy 40 points
Other Parts Discussed in Thread: LMV797, LMV796

Hello, I'm trying to simulate the LMV796/797 op-amp in SPICE and I'm running into a model where the op-amp rails on the positive end at 4.1V. It's a rail-to-rail amplifer, so I expected that rail to be higher. The negative rail is around 37mV, which makes more sense. Did anyone else have this issue? I used the PSPICE model from the LMV797 product page for this. Also tried this in Multisim (which has a model for it) and it also rails at 4.1V. Any help would be appreciated.

  • 0
    TI__Guru 53036 points

    Hello Ashiful,

    The SPICE model is working correctly.

    The LMV79x family is Rail to Rail output, but NOT input. The output will swing millivolts to either rail, but the input can only swing from V- up to 1V below the V+ rail.

    You did not mention your circuit, but I will assume it is a simple follower. While the output can swing rail-to-rail, it is limited by the input stage limits (0-4V).

    If you want the output to swing the full 5V, then you will need a Rail to Rail input device (which are almost all rail to rail out by default).

    Regards,