I'm designing active electrodes for surface EMG, active electrodes being electrodes directly connected to a pre-amp and filtering stage on the measurement site.
Im working with the AD8221 IN-AMP to pick up the differential signal and I am trying to eliminate the need for a reference electrode by driving the reference pin of the IN-AMP via a voltage divider and buffer to bring the AD8221 to midsupply level.
However with my simulations I have failed to receive the desired midsupply voltage level at the reference pin and infact only get a few hundred millivolts. Can someone please explain to me the theory of operation with the reference pin? and whether this method will effectively eliminate the need for the reference electrode?
+/- 5V power supply for the entire circuit.
Gain = 100. (Rg = 499 Ohms)
I have read through the other threads related to my topic, but none have encountered the problem I have. I am running a simulation on MultiSim v.13
Update: the current schematic