AD8237 or AD620?

A project log for EyesDrive

An innovative, non-invasive, assistive Human Interface Device for ALS affected people based upon Electrooculography (EOG) technique.

Federico RuncoFederico Runco 08/25/2019 at 20:480 Comments

Currently the preamp is an AD620, it's quite good and pretty easy to use, but i think is only good for a prototype.

Now that I'm waiting for the first prototype PCB, I'm designing the version n. 2 and I'm thinking about switching to a more accurate Instrumentation Amplifier. The AD8237 seems the right successor: it's rail to rail, zero drift, low voltage (minimum 1.8v vs 5v required by the AD620) and a 115uA maximum current consumption. It seems the right one, the only doubt is how can I derive the common mode voltage, in the AD620 i simply get the average with some resistors on the gain pins, I can do the same thing in this one, but I must do it in the input pins, and it would reduce the input impedance; I'll think about it for the next days.