Can AD8293G80 measure below GND?

Hi HansWurst07,

AD8293's Vs- is recommended to be connected to GND as seen in the part's IVR spec. In its simplified internal schematic, Vs- is also connected to GND. Using the part beyond the specified specifications in the datasheet would not guarantee its performance and may damage the part.

Could you share what are your requirements? We can take a look at it and may suggest a better part for your application.

Thanks,

Kristine

Hi Kristine,

I tried to paste the schemtic here yesterday thank. you for doing this :-)

The requirement is "only" to extend the common-mode input range 200mV below GNG/Vss (what you like to call it here). Single supply of 5V, Gain between 80 and 90, bandwidth ~100 Hz, input offset error below 100µV (including possible resistors). The AD8293 is so tiny, relatively cheap that it's really a pity to not have a simulation model for it to try it out...
Judging from the afore mentioned schematic the intput FETs should not care at all if the input is some mV below GND (and it is quite common; until ESD protection diodes start to conduct).

Thank you for your input!

Hans

Hi HansWurst007 ,

It seems that the AD8237 can do the job.

Check it with the very useful simulation tool on the ADI website called Instrumentation Amplifier Diamond Plot Tool.

Zoltan

Thank you for this hint to the 8239. In total in requires to more low drift resistors and is a bit mit expensive itself. But yes, it might do the trick :-). Thanks again