Hello, i'm designing an ECG amplifier(to amplify the electric heat signal). My ADC reference voltage is 3.3V, so assuming that ecg signal is ~3mV i need a gain of 1000. The heat of this project is instrumential amplifier AD8221. (datasheet - http://www.analog.com/static/imported-files/Data_Sheets/AD8221.pdf) ECG signal bandwidth is 0.05Hz - 150Hz, diferential amplitude 1-5mV with a DC component od 0.3V which limits first stage gain. First stage has a gain of 100.The feedback integrator(U3,R4,C4) that drives ad8221 reference pin should cancell out DC component.R4 and C4 were selected for the integrator to output voltage only if there is DC component (0.05Hz threshhold). The last stage is active filter with a cutoff frequency of 150Hz and a gain of 100. Tell me what do you think about my design!