Hi Neil,

Thank you very much for your reply.

The provided information is really helpful to me. As you suggested I have decided to use ADA4941( similar to ADA4940 ). I am using ADA4941 (single to differential converter) as similar to the architecture suggested in the datasheet of AD7982(Page:15, Figure : 26).

The datasheet of ADA4941 doesn't provide the following information.

1. There is no suggestion for selecting the proper external resistors. I need some information about the tolerance and drifts of external resistors to be used. Please suggest some of resistors which suits for ADA4941.

2. The gain error of ADA4941 is mentioned as +/-1% for a gain of 2. Is it the intrinsic gain error associated with ADA4941.

Thanks,

Jebas.

Hi Jebas,

I have branched this thread to another subject.

1. I think most amplifier datasheet does not include the effects of external real resistors. For common amplifier equations such as the non-inverting gain of 1+Rf/Rg, both external Rf and Rg are considered ideal. To find out the effects of their tolerances, you need to include the tolerance in the equation. This way you can predict the behavior of your circuit with these real world components. And for the drift errors, you want to have the minimum drift errors from your external components so that only the amplifier drift parameters will dominate. Otherwise, having large drift errors from external components will degrade the drift performance of the amplifier used.

An EDN article talks about worst-case circuit design including component tolerances.

2. Yes, that is the intrinsic gain error of the ADA4941 based on the internal resistors that developed G=2.

You may also want to read CN0032, which discusses the ADA4941 driving the AD7982 ADC.

I hope this information is helpful.

Best regards,

Neil