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LM2904B-Q1: Fault reported when voltage difference is small

Frank QIN
Genius 9490 points
Part Number: LM2904B-Q1
Other Parts Discussed in Thread: LM2904, LM358

Tool/software:

HI Team,

While working on the LM2904B-Q1 Spice model, we want to build a differential operation amplifier simulation. And the op amp expected output is Vo=0.33*(V10-V11).

When the supply power is 16V, the voltage difference between V10 and V11 is not that large, there would be fault reported, as the log showed.

When the voltage difference between V10 and V11 is large, there is no fault.

When supply voltage is lower than 9V, any voltage difference between V10 and V11 are as expected.

We would like to learn about the reason behind this. Why it would report fault when voltage difference is small.

Thanks

Regards,

Frank

  • 0
    TI__Guru* 77541 points

    Hi Frank, 

    Frank QIN said:
    We would like to learn about the reason behind this. Why it would report fault when voltage difference is small.

    Yes, there is an issue with the existing LM2904/LM358 Spice model, see the simulation below. 

    LM2904B-Q1 E2E 04102025.TSC

    If I connect the 1Mohm load, then the circuit is operating in non-linear mode, which is an issue. 

    If I use an ideal op amp to replace the LM2904 Spice model, then it is working properly. So the LM2904/LM358 Spice model has issues. 

    Frank QIN said:
    we want to build a differential operation amplifier simulation. And the op amp expected output is Vo=0.33*(V10-V11).

    Here is the simulation for the difference amplifier, which it seems to be correct. Anyway, there are issues with the Spice model. I will ask our modeling engineer to take a look. 

    LM2904B-Q1 DA E2E 04102025.TSC

    Best,

    Raymond