HELP = ECG circuit problems..........

help with circuit problems

i'm now doin research on ECG circuit. i dun really understand one of the ECG part,amplifier+filter part. the part containing Differential amplifier+2nd order BPF+inverting amplifier+summing amplifier.

can someone tell me why...
-we need inverting amplifer?why cant we jus amplify the signal during differential ampifier then pass to BPF filter out the noise then ok de
-why we use 2nd order BPF instend of 1st order?wat is the different


thx for answering my topic !!!!!

ecg circuit

hi

darlling5147 said:

can someone tell me why...
-we need inverting amplifer?why cant we jus amplify the signal during differential ampifier then pass to BPF filter out the noise then ok de

Click to expand...

You don't need an inverting amplifier, it depends on the design.
One of the recommendations of the American Heart Association is that an ECG should tolerate offsets of 200mV (that is for the offset developed at the skin-electrodes interface), so many designs split the overall amplification in a first low gain DC-coupled stage at the input of the electrodes and after a high pass filter they amplify again to reach the overall amplification required (around 1000).

darlling5147 said:

-why we use 2nd order BPF instend of 1st order?wat is the different

Click to expand...

That is for aliasing. The order of the filter depends on the quality of the signal that you want to acquire (it depends on the type of application), the Fc and filter order, the sampling frequency and the number of bits of your AD. There is an interesting pdf about this at www.analog.com (I could upload it if you want).