INA188: Drift and noise

Alex Chen

Part Number: INA188
Other Parts Discussed in Thread: INA818

Tool/software:

We need an instrumentation amplifier to interface an input signal with a 24-bit ADC, prioritizing low drift and 1/f noise for stable voltage measurements. We evaluated the INA188 and INA818. The INA188 is a zero-drift amplifier, yet its offset voltage (25 µV) is higher than the INA818’s (10 µV), despite similar drift. Both have comparable output noise (2.5 µV) from 0.1 Hz to 10 Hz. Why does the zero-drift INA188 have a higher offset voltage, and which amplifier is better suited for our application?

3 months ago

0 Kevin Chen 3 months ago

TI__Prodigy 390 points

Hi Alex,

The INA188 would be better suited for your application. The zero-drift architecture provides the low drift and low noise that you are looking to prioritize, and the larger offset voltage can be calibrated out. The differences in offset voltage between INA188 and INA818 can be attributed to differences in architecture (zero-drift versus super-beta input). There is also a similar form asking about comparisons between the two devices that may be helpful to you: https://e2e.ti.com/support/amplifiers-group/amplifiers/f/amplifiers-forum/1037119/ina818-offset-voltage-drift-compared-to-ina188-85c

Best,

Kevin

0 Alex Chen 3 months ago in reply to Kevin Chen

Prodigy 10 points

Thank you for your response. The data sheets indicate that the input offset voltage (Vosi) of the INA188 and INA818 is similar at 0.4µV/°C, but the output offset voltage (Voso) varies significantly (INA188: 0.35µV/°C, INA818: 5µV/°C). What accounts for this difference in Voso? Additionally, how are Vosi and Voso measured?

0 Kevin Chen 3 months ago in reply to Alex Chen

TI__Prodigy 390 points

Hi Alex,

The difference in Voso can be attributed to the differences in their output stages. Although they have similarly high performing input offset drift, their different architectures would result in prioritizing different characteristics. In this case, the INA188 zero-drift architecture achieves a low output offset voltage.

The test conditions for the electrical characteristics can be found at the top of the page:

For more information on measuring offset voltage, we have this application note as well as our TI Precision Lab on offset voltage.

Best,

Kevin

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INA188: Drift and noise