I Have designed a circuit to acquire the EEG signal from electrode within 0-20 microvolt. My design consists of AD620 (gain = 2), -> LPF (4th order G=2.515, Fc= 0-40Hz),-> HPF (4th order G=2.515, Fc = 0.1 to 40 Hz), -> Two stage amplifier with G=180. But I am getting a constant output at AD620 of 1.28V without or with input connected. And the output after LPF filter HPF, and two stage amplifier is found to be 4.78V constantly.
I am not getting why this error persists. I have checked my PCB and it is ok connection wise. So it will be of great help if you can tell me the error?
I want to acquire EEG signal to make it in acceptible limit of ADC of 0-5V.
I want to give the acquired EEG signal to 24 ADC and then toARM Cortex M3 for further processing.