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WEBENCH® Tools/OPA376: Noise simulation and/or calculation for a voltage follower op376 vs LMP2021

Bernd Hafen
Prodigy 50 points
Part Number: OPA376
Other Parts Discussed in Thread: LMP2021, TINA-TI,

Tool/software: WEBENCH® Design Tools

Hi,

I want to calculate the noise using op376 vs LMP2021 to make a vmid from the power supply.

At OP+ I have a resistor voltage devider with 10k, so where to put the noise source? (See more in attached Tina-Ti schematic)

Best regards

Bernd

OPA376_VMID.TSC

  • 0
    TI__Guru 60590 points

    Bernd,

    You can place the input voltage source wherever you want.  The only reason for the source is to identify the magnitude of the input referred noise at a chosen input node (the source itself has no noise) - see below.

    The graphs below in first row show correctly output noise for different values of input resistors.  The graphs below in a second raw show corrupted output caused by non-linear operation of OPA376 (I can't read the second schematic but most likely output is slammed against one of its rails).

    Below please see the voltage noise spectral density comparison of OPA376 vs LMP2021 in a follower configuration using +/-2.5V supplies in order to eliminate the need for the input resistors, which themselves contribute the thermal noise (1kohm=~4nV/rt-Hz noise).

    For your convenience, I have attached below circuit schematic.

    OPA376-LMP2021 noise.TSC

  • 0
    Prodigy 50 points

    Hi Marek,

    thanks, for the help and the hint how to compare OP-Amps!

    "the corrupted output" you mean, happens when I put a seriel resistor (20k//20k) between Vin Source and +OPInput, the result I don't understand, why this should be wrong!

    Best regards

    Bernd