Dear Sir,

In my application I am using the instrumentation amplifier AD8237, now I need to calculate the total noise of the circuit. But as referring to application note for calculating Total noise of INA at a given gain the value of eni and eno is needed which is not mentioned on the data sheet of AD8237. Where as this value is given in the datasheet of the other parts. The datasheet of AD8237 mentioned the noise voltage and current noise.

SO please let me know how to calculate the above values.

Thanks

Hi Sameer,

The AD8237 has a different internal architecture compared to earlier instrumentation amplifiers. The earlier in-amps have a 2 op-amp or 3 op-amp architecture, both of which have two stages with different gains to the output. This is the reason why they need to have Eni and Eno specifications.

The AD8237, on the other hand, will generate noise internally just like an op-amp. The voltage noise referred to the input should remain constant (refer to page 3 of the datasheet), while the voltage noise referred to the output will just be the specified voltage noise multiplied by the external gain applied. Generally, calculating the noise for an AD8237 circuit which uses passive components to set the gain will be the same as calculating the noise for an op amp in a non-inverting configuration.

I hope this helps!

Kris