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INA240: definition difference of input offset between INA240 and INA188

Jerry Chen
Expert 5110 points
Part Number: INA240
Other Parts Discussed in Thread: INA188,

Hi,

Compared with INA188, the power supply for INA240 is very simple, so I don't think it is a general amplifier. It must have a resistance network at the input to attenuate the input common voltage. 

I want to use it in a high side shunt current sensing application. I could use either INA240 or INA188. The offset of INA240 is 25uV, and it is 55uV for INA188. Does it mean offset of INA240 is really smaller than INA188? If their definitions are same(apple to apple), I think INA240 has more advantage with simpler power supply and smaller offset.

Thanks.

  • 0
    TI__Mastermind 21720 points

    Hello Jerry,

    Thanks for reaching out on the forum. If we do an apple to apple comparison then this is how voltage offset referred to the input would look according to the gain:

    Gain (V/V)

    INA240 Vos_max (V)

    INA188 Vos_max (V)

    20

    25μ

    55+170/20= 63.5 μ

    50

    25μ

    55+170/50=58.4 μ

    100

    25μ

    55+170/100=56.7 μ

    200

    25μ

    55+170/200=55.85 μ

    So you are correct, in that the INA240 has better offset. The % error from offset for each respective part can be calculated from the formula below.

    Another benefit of the INA240 is that it has higher bandwidth for each respective gain. Lastly the swing to gnd and swing to VCC for the INA240 is smaller than the swing to rail on the INA188.

    However, the one specification where the INA188 surpasses the INA240 is on input bias current, yet you may have to make your INA188 V- pin go below ground to enjoy that benefit. The % error from input bias current for each respective part can be calculated from the formula below.