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OPA4991: output Swing at full temp range

Yang Wu
Expert 3120 points
Part Number: OPA4991
Other Parts Discussed in Thread: OPA4171,

Tool/software:

Hi Team,

I am promoting OPA4991 to replace OPA4171 in my customer.

The DS of OPA4991 only gives output swing @25 degrees of Vin = 2.7V or 40V.
Do you have the min/typ/max data @ full temp TA = –40°C to 125°C of Vin = 5V, RL = 10Kohm? If you don't have the data, do you have some methods to estimate it? 

In addition, for OPA4171, it only gives typ output swing @25 degrees of Vin = 5V, RL = 10Kohm. Do you have the min/typ/max data @ full temp TA = –40°C to 125°C of Vin = 5V, RL = 10Kohm?

Thanks a lot.

Best regards,

Yang

  • 0
    Guru 287360 points

    Figures 6-14/15 show how the typical drive strength changes with temperature. You can estimate by applying the same factor to the guaranteed worst-case limits.

     

    The OPA4171 datasheet has a similar graph in figure 5-9; the behaviour is essentially the same. To estimate min/max values, compare the typical and min/max values of the OPA4991.

  • +1 in reply to Clemens Ladisch
    TI__Guru 54996 points

    Hi Yang, 

    As Clemens has correctly explained, Section 5.9 (on the OPA4171 data sheet) or Section 6.8 (on the OPA4991) show the Typical Characteristics, including for the output swing vs load at different temperatures; and provide a good overview of the output swing behavior vs load and temperature conditions.  It is also important to understand, that these output swing curves and the "Voltage output swing from rail" spec on the data sheet represent a condition where the output stage is saturated, with the amplifier output stage reaching as close to the supply rail as possible, outside the  op-amp optimal linear region. This is in general true for most op-amp data sheets. Nevertheless, using these curves while adding additional headroom allows to obtain an estimate of the amplifier output range.

    A conservative approach, while keeping the amplifier well within the optimal linear region, use the OPA4991 AOL (open-loop voltage gain) output swing test condition.  On this test, the amplifier output stage is not saturated, with the device still operating well within the linear region. The OPA4991 device specifies the AOL with a 10kΩ load over the extended temperature range from -40C to +125C, where the device requires 100mV headroom from the rail supplies.

    If you compare to the OPA4171 AOL output swing condition, the amplifier requires a larger 350mV headroom from the rails with a 10kΩ load over the extended temperature range from -40C to +125C.

    You can learn about the op-amp output swing specifications on the attached application note. Section 9 "Linearity of Output Swing Limitations" on page18 and Section 10 on page 19 may be of interest.

    Op Amp Input and Output Swing Limitations

    Thank you and Kind Regards,

    Luis

  • 0 in reply to Luis Chioye
    TI__Expert 3120 points

    Hi Clemens, Luis,

    YES, I agree with you. I also showed the method that Clemens mentioned. while also thanks for the AoL method to make sure we have enough margin.

    Best regards,

    Yang