INA188: GAIN setting

Kuramochi Tadahiko

Guru 28715 points

Part Number: INA188

Hi,

49.9Ω is recommended as GAIN=1000.

When RG = 49.9Ω, Actual GAIN is 1003.

Otherwise, Gain range shows 1~1000 on the specification.

Gain is not guaranteed when RG is 49.9Ω.

Is it correct?

Best Regards,

Kuramochi

over 6 years ago

0 Errol Leon6 over 6 years ago

TI__Expert 5830 points

Hello Kuramochi,

the datasheet is showing that to have a gain of 1000, the RG value needs to be 50.05 ohms. Looking at standard resistor values with a tolerance of 1% the closest value is 49.9 ohms. With a tolerance of 1% the two worst case gains with a 49.9 ohm resistor would be a gain of 993.08 (RG=50.399 ohms) or 1013.13(RG=49.401 ohms). These worse case values can be reduces by using smaller tolerance resistor such as 0.1% tolerance.

Best regards,

Errol Leon
Texas Instruments
Precision Amplifier Applications

0 Kuramochi Tadahiko over 6 years ago in reply to Errol Leon6

Guru 28715 points

Errol-san,

Thank you for your support.

Though gain overs specified gain(1~1000), setting RG to 49.9 ohm(Gain=1003) is no problem.
Is my understanding correct?

Best Regards,
Kuramochi

0 Errol Leon6 over 6 years ago in reply to Kuramochi Tadahiko

TI__Expert 5830 points

Kuramochi-san,

That is correct.

Best regards,
Errol

0 Kuramochi Tadahiko over 6 years ago in reply to Errol Leon6

Guru 28715 points

Errol-san,

Thank you for your quick answer.

I have an additional question.

Why is maximum Gain range specified 1000 nevertheless gain can be set over 1000?

Best Regards,
Kuramochi

0 Zak Kaye over 6 years ago in reply to Kuramochi Tadahiko

TI__Mastermind 23050 points

Kuramochi-san

The gain specification in the datasheet just means that is the maximum gain for which datasheet performance is guaranteed. You can operate with higher gains, but the device is not tested at these operating points. In gains greater than 1000 you may start to see higher gain error, but the device will still function as intended.

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INA188: GAIN setting