INA819: How to calculate the error value of Table5

Takumi Suzuki1

Mastermind 8610 points

Part Number: INA819

Hi,

Let me ask you a basic question about "Table5 Error Calculation", datasheet page25.

I do not understand how to calculate the error value.

For example, about input offset voltage, in case G=1, the error is 35ppm. Why 35ppm (not 35uV) ?

And about "Voltage noise", why the error is 1204ppm @G=1 ?

Though I tried to calculate the value by the reference equation, I could not reach the value, "1204".

Thank you for your support.

Best Regards,

Takumi

over 3 years ago

+1 Tamara M Alani over 3 years ago

TI__Genius 10850 points

Hello Suzuki-san,

Thank you for your post, I can help you.

The input offset voltage is indeed 35µV, not 35ppm. If there is a unit in the column labeled "UNIT" then we use that unit. If there is no unit listed in that column, we assume ppm.

In regards to voltage noise, there is a calculation error in the table. The correct answer is 735ppm. Let us follow this equation:

Where:

sqrt(BW) = noise bandwidth = kn * fc where kn is the Brickwall correction factor. For this INA, it looks like the roll-off is -60dB at G = 1 V/V. That means the kn correction factor is 1.16 so sqrt(BW) = sqrt(1.16 * 2MHz)