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INA851: Unity gain bandwidth

Lucy Fanelli76
Prodigy 110 points
Part Number: INA851


Tool/software:

Can someone tell me the unity gain bandwidth or gain bandwidth product of the input-stage opamps in the INA851? It doesn't appear to be in the datasheet and I'd like it for design purposes.

Thanks,

Lucy

  • 0
    TI__Guru 55466 points

    HI Lucy,

    The INA851 input stage does not incorporate a traditional two op-amp input stage; so I don't believe you can define the gain bandwidth product as a general op-amp. Also, in general, on most instrumentation amplifiers, even the ones that use a traditional 3-amplifier architecture, do not provide a spec for gain bandwidth product, but only provide the gain as a function of frequency.

    The INA851 incorporates a current-feedback input stage, and a four-resistor fully differential output stage.  Figure 8-1 of the data sheet shows the block diagram. If you notice, the current feedback differential input stage has fewer devices than a traditional amplifier input stage, hence, this topology tends to offer better DC precision vs the traditional due to fewer sources of error at the input.  It also tends to provide lower input referred noise and higher slew-rate for the same power consumption, when compared to the traditional input stage.

     

    If I remember correctly, the bandwidth of the FDA output stage at G=0.2 is around ~22MHz.  The Gain vs Frequency plot on Figure 7-24 shows essentially the bandwidth of the input stage at G=1 at around 15-MHz.  Please see below.  

    Thank you and Regards,

    Luis