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OPA847: Thermal drifts? (of input resist., input capacit. and gain-BW prod.)

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Replies: 3

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Part Number: OPA847

Good afternoon

It would be of great help if you could kindly provide us any information about the thermal drifts of the following parameters (for the O.A.s mentioned below):

  • Input resistance (differential and common modes)

  • Input capacitance (differential and common modes)

  • Gain-Bandwidth product (GBP)

The O.A.s are: OPA847, LMH6624, THS4021. All of them have high GBP which is a key figure of merit to achieve low phase drift values due to the AO, which is the main issue in our work.

In the case of the LMH6624, an Open Loop Frequency Response Over Temperature figure is included in the datasheet. Nevertheless, we cannot deduce any feasible information due to the proximity of the plots.



Thank you very much in advance.



Kind regards



Ernesto

  • Hi Ernesto,

    Unfortunately, those are not parameters we take during our typical characterization measurements. Is there a reason this is a specific concern to your application?

    Best regards,

    Sean
  • In reply to Sean Cashin:

    Hi Sean, thanks a lot for your fast answer.

    In relation with our research activity (at the Electronics Department of the University of Alcalá, in Madrid, Spain), we have designed a transimpedance amplifier with the O.A OPA847 (for an indoor robot positioning Infrared sensor). This O.A.-based I/V converter receives a 6 MHz sinusoidal intensity-signal from a photodiode. After some further stages we measure phase-shifts from this signal(s).

    So: in our application, a key issue is to know (in order to limit) the phase thermal drifts of the photodiode current, due to the O.A. Our theoretical analysis shows that these phase thermal drifts can be obtained as a function of the O.A. parameters mentioned in the previous post (i.e. Input resistance, input capacitance, and Gain-BW product) which, as you mention, we could not find in technical available information.

    Thanks again,

    Kind regards

    Ernesto

  • In reply to user5141858:

    Hi Ernesto,

    Typically the values for input resistance and capacitance can vary about +/-10% from the datasheet across process variation and temperature, as with the GBW as well.

    Best regards,

    Sean

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