AnsweredAssumed Answered

AD8420 ECG application

Question asked by libuz on Jul 11, 2012
Latest reply on May 7, 2013 by ScottH


I am trying to design an ECG amplifier with AD8420, which will be connected to ADC. And later I want to use it for smaller signals like EEG. I am trying to implement this circuit from the data sheet. And I have some questions regarding this

1. I tried to change the gain to 1000 by replacing 100k with 1M. But it didn't show much difference. Is it possible to  increase the gain more than 100. (my low pass cutoff is at 150Hz)

2. Since the input bias current of this IN-amp is quite higher that others, will that be a problem? i don't know much about the effect of input bias current. Could you explain a bit.

3. Since we are getting first stage gain of 100 with CMRR of 100, how much difference does it make if I implement DRL method on this circuit.

4. Since my ADC reads only positive, I want to use it with single supply. So I replaced -5V supply of both ICs with ground. But it doesn't work. How can use it with single power? 

5. Datasheet says, the servo integrator high pass filter is 0.5Hz. My calculatio shows that it is 0.005Hz.


Thank you.