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LME49810 input impedance and input bias currents

Per-Anders Sjöström
Prodigy 250 points


Missing info in the datasheet of LME49810

Input impedance

Input bias offset current

Can you give any hint about these values?

  • 0
    TI__Guru 52115 points
    I will try to find this info for you.
  • 0
    Expert 1220 points

    The input bias current is stated to be 200nA max and 100nA typical. This tells me that the input structure is bipolar. This also tells me that the input bias current offset will be on the order of nA; most likely in the 10's of nA.

    As as SWAG, the input impedance will be close to 100kΩ||5pF.

    -Ken

  • 0
    TI__Guru 52115 points
    Hi Peranders,

    Here are some comments I got for you:
    "a) Regarding the input impedance, it depends on the operating condition.
    i) If it is open loop condition, the input impedance between In+ and In- will be about 5.12k to 10.24k ohms.
    ii) If it is closed loop condition, it will be multiply about feedback amount. For example, if the feedback amount is 40dB, the input impedance will be about 100 times of the open loop input impedance.

    b) Regarding input bias offset current, it will be about 2% of input bias current. In this case 100uA of input bias current in typical value, so the input bias current offset is about 2nA typ and 4nA max. But this is not guaranteed."

    Andy
  • 0 in reply to Andy Liu (BMS)
    Prodigy 250 points

    You mean nano amps, I'll suppose?

    Anyway, thanks for the info. Maybe you should add this info into the data sheet?