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Original question:

AD8421BRMZ CMRR Failure

INA821: INA821 Slew rate

Varunesh Kumar
Intellectual 795 points
Part Number: INA821

Hello 

Sometime back Mike asked about an Analog Device AD8421 

to which you suggested INA 821 .

The Bandwidth of INA 821 at Gain of 1 is specified as 4.7 MHz ;

yet the Slew rate is only 2 V / uSec for the same conditions ;

while AD8421 specifies a Bandwidth of 10 MHz and a Slew rate of 35V / uSec

Can someone please elaborate on this ?

Thanks 

  • 0
    Guru 140200 points

    Hi Varunesh,

    Leonard very probably searched for "comparable supply voltage", "comparable maximum input offset voltage" and then, finally, for "highest speed" and found this:

    Kai

  • 0
    TI__Mastermind 47616 points

    Hi Varunesh,

    Interesting. Do you have the thread regarding to - " 

    Sometime back Mike asked about an Analog Device AD8421 to which you suggested INA 821 ."?

    I think that there may be a mistake somewhere. AD8422 and INA821 are very similar, and I can believe that someone suggested the replacement. AD8421 is  higher BW and high slew rate part.  

    Best,

    Raymond

  • 0 in reply to Raymond Zhang1
    Intellectual 795 points

    Hi Raymond 

    The original Q was raised by Mike Thornhill under Sub headline 

    "AD8421BRMZ CMRR Failure ""

    perhaps without realizing that the device he was asking about was not TI's

    but Analog Devices .

    I do not have any Ref No of that query ; but Leonard has replied to that thread

    on Jan 10th ; 2020 ; 8:54 PM as follows ;

    " 

    Hello Mike,

      Thank you for your inquiry on Texas Instruments E2E, but the device you are asking about is an Analog Devices part; therefore, we cannot comment.  

    If you would like to replace the AD8421 with a TI device, please look at the INA821.  You can view a comparison of the two devices here: https://bomcross.ti.com/en/compare/AD8421BRMZ---Analog%20Devices%20Inc--vs--INA821IDGKT---Texas%20Instruments%20Inc . 

    I hope you find the INA821 a much better choice and use it in your design! 

    At your service,

    ~Leonard "

    My question was reg the definition of BW and the Slew Rate of INA821 .

  • 0 in reply to Varunesh Kumar
    TI__Mastermind 47616 points

    Hi Varunesh,

    I see your point. I agree that we need to be more diligent in providing a suitable suggestion. 

    I'd consider that the  suggestion was a mistake. However, the post did imply that " please look at the INA821". The ultimate decision has to be made by the inquirer, who is an engineer. 

    I am going to close this inquiry, since I am speculating on the post. It is what is and I am unable to elaborate it further. 

    Best,

    Raymond