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LMV881: Offsetvoltage

Prodigy 40 points

Replies: 9

Views: 599

Part Number: LMV881

When the Voltage at the positive Input (pin 1) is about 0 to 2 Millivolts, the output (pin 4) is about 72 mV.

The voltage on the output has an offset, that seems greater than what one could expect (as from datasheet)

What could be the reason for that?

  • Hi Christoph,

    the LMV881 cannot fully go down to 0V at the output. One fix is to add a small negative supply voltage by using the LM7705.

    Kai
  • In reply to kai klaas69:

    Hi Christoph,

    Thanks for your interest in our part, my name is Mamadou Diallo, I am application engineer here in GPAmps.

    To add to Kai suggestions, please consider using a Vee=-0.2V and take measurements on pin-4 with pin-1 grounded and with a voltage on pin-1.

    if your application cannot handle high offset, I can help refer other devices, in addition to LM7705, with lower offset voltage.

    Regards,

    -Mamadou
  • Thank you for the responses!

    When I remove R61 and short R60 the output is about 0.3 mV while the input is about 0.1mV.
    Why is the behavior that different to the original circuit?
  • In reply to Christoph Hofer71:

    Hi Christoph,

    because now no load current must be driven. Have a look at figure 11 of datasheet.

    Kai
  • The current to get 72mV must be a few mA i assume. (Not shure, because the y-axis is labelled in an unusual way)
    In my case I think there are only few uA.
  • In reply to Christoph Hofer71:

    Hi Chjristopher,

    figure 11, I mentioned, is only valid with RL referenced to V+/2. So, take it not too literally, read between the lines to get an idea of why the output signal can furtherly go down to 0V when the load current is decreased... :-)

    Kai
  • In reply to kai klaas69:

    Hi Christoph,

    Since we have not heard back from you, we must assume you've resolved your issue, so I am going to mark this thread as such.

    If you HAVEN'T solved it, please feel free to post more questions, and we will help you resolve it.
    If you HAVE solved it, you can share how you did so, in order for other future users to benefit from your answer.

    Thanks!

    Regards,

    -Mamadou
  • In reply to Mamadou Diallo:

    Hello

    I resolved this with R60=2k and R61=2k. With this circuit the output is below 1mV (when the input is also well below 1mV).

    Regards,

    Christoph

  • In reply to Christoph Hofer71:

    Glad to hear that your circuit is working!

    Thank you Christoph for sharing!

    Regards,

    -Mamadou

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