Hello,
We are working on ECG application of INA333 and OPA333.
We are having a few problems as follows-
1. INA333 Gain - Theoretical gain does not match practical gain.
Equation given in datasheet cannot be verified practically.
for Rg=5k, Vin= 20mVp-p Sinewave + 0.5V DC offset --> Vo=75mVp-p 2.5 V DC offset.
Expected gain= 21, Actual gain= 3.7
(pl refer attached PDF for schmatic design)
2. LPF Filter designed for Gain=100, in circuit gain=75. What could be the reason for this?
3. We have included notch filter of 50Hz after the gain stages. Should it be present before amplification?
How else to reduce dominant 50Hz signal by hardware?
4. What testing precautions should be taken in order to get perfect ECG waveform on DSO?
5. What is expected output nature of signal at Right leg drive and shield?
Awaiting your response,
Thanks,
Anish