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OPA2156: Absolute maximum rating for differential voltage

sang hoon Kim
Prodigy 30 points
Part Number: OPA2156
Other Parts Discussed in Thread: TIDA-00777, OPA828, OPA827, OPA2727

I am considering using OPA2156 as an active integrator. I would like to ask what the absolute maximum ratings for signal input pins' voltage differential means in the datasheet.

Does that mean the voltage across + terminal and -terminal of the ampifier? If so, the differential voltage should be less than 0.5 V while operating?

I refered to TIDA-00777 to design op amp-based active integrator, where low offset, offset drift, bias current, and voltage noise density are important factors. Considering these, I found that OPA2156 is good for our design. Our target is as follows: GBW > 20 MHz, max. differential voltage = 2 V. If it is true that the differential voltage is limited to 0.5 V, I have to search for other op amps. If you do not mind, could you please recommend suitable op amp options that have similar features of OPA2156? I am also considering OPA2727 as an alternative. I look forward to your reply. Thank you.

  • 0
    TI__Guru 63010 points

    Sang,

    The OPA2156 maximum input differential voltage DIRECTLY between the input terminals is 0.5V (see back-to-back input protection diodes) unless you limit to current with an external resistor to 10mA or less - see simplified schematic below.

    In the normal linear operation all op amps, including active integrators, maintain a virtual short between the inputs and there is no risk of 2V differential voltage directly between the input terminals - see below.  Only under non-linear operation where output is pushed against the rail the op amp may not be able to maintain the virtual short BUT as long as R1/RF resistors limit the current to 10mA or less, there is no danger of damaging the op amp - see below.

  • 0
    TI__Guru* 93105 points

    Hello Sang Hoon,

    In addition to Marek's explanation here are two high performance JFET input op amps that have a differential input voltage equal to the supply voltage +/-Vs; OPA827 and OPA828. Do note that they are only available as singles. You can view their datasheets here:

    www.ti.com/.../opa827.pdf

    www.ti.com/.../opa828.pdf

    The OPA2727 should do what you need and is a dual op amp, but keep in mind the maximum supply voltage should be kept to +/-6 V.

    Regards, Thomas

    Precision Amplifiers Applications Engineering

  • 0 in reply to Marek Lis
    Prodigy 30 points

    Dear Marek,

    Thank you so much. I just forgot to consider R1 from the figure of active integrator. Now that I understand that there is no danger for differential voltage rating, I will try to use OPA2156.

    Best,

  • 0 in reply to Thomas Kuehl
    Prodigy 30 points

    Dear Thomas,

    Thank you for your answer and suggestions. Those looks good as well. I may go over those op amps if I need, for now, I will try to use OPA2156 first.

    Best,