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TLV9001: Input impedance of TLV9001

Frank Cai
Intellectual 1105 points
Part Number: TLV9001
Other Parts Discussed in Thread: OPA310, OPA2310

Hi team,

I would like to check with you, if we have the data for input impedance for TLV9001? I could see OPA310 has the both resistance//capacitance but I can only find input capacitance in TLV9001. Thank you

Sincerely

Frank

  • 0
    TI__Mastermind 23200 points

    Hi Frank,

    How very strange. Thank you for pointing this out to us. This got me to check and I noticed that the other TLV90xx device families also only show the input capacitance. 

    With this being a CMOS input architecture op amp, the input impedance is going to be in the 100's of Megaohms, to gigaohm levels. I can see if we have ever taken this data if you need to get a closer estimate. However I've found most of the time the input resistance only really matters if the op amp is using bipolar transistor architecture since CMOS impedances are so high.  

    Let me know if you need more information or if this would be sufficient. 

    Best Regards,

    Robert Clifton 

  • 0 in reply to Robert Clifton56
    TI__Intellectual 1105 points

    Hi Robert,

    Thanks for the explain.

    My customer is now wondering if TLV9001 can fulfill 50G Ohm input impedance, it is a requirement for their application. So I would like to double check with you if TLV9001 can fulfill it or not.

    If not, I will propose other device such as OPA2310 which clearly indicate the device input impedance.

    Thank you.

    Sincerely

    Frank

  • 0 in reply to Frank Cai
    Guru 271570 points

    As far as I know, all datasheets specify the input bias current, so it might be more productive to use this limit.

    For CMOS devices, the input current is just a leakage current and depends mainly on temperature; this behaviour is not accurately described by just an impedance value:
     

  • 0 in reply to Clemens Ladisch
    TI__Mastermind 23200 points

    Hi Frank,

    Clemens is right. Most of the time, customers care more about the input bias and offset current rather than the input impedance. Is their a specific reason the customer is wanting to know if the input are 50Gohm? 

    Best Regards,

    Robert Clifton 

  • 0 in reply to Robert Clifton56
    TI__Intellectual 1105 points

    Hi Robert, Clemens,

    Yes, 50G Ohm is customer's specific requirement. So we need to know if TLV9001 can fulfill it or not.

    I can understand the input bias current can be taken in consideration, actually, customer need the input bias current in pA level is okay.

    Sincerely

    Frank

  • 0 in reply to Frank Cai
    TI__Mastermind 23200 points

    Hi Frank,

    Still waiting to hear back from the design team to get the input impedance values. It might be till Friday before we hear back from them. 

    Best Regards,

    Robert Clifton 

  • 0 in reply to Robert Clifton56
    TI__Guru*** 145766 points

    Frank,

    In chart I see less than 1pA over 5.5V ; 5.5T ohms ; this is just typical. 

    50G is 100pA over 5V ; TLV9001 should be able to achieve this. A rare outlier is possible because this is not tested .