Problem with ECG amplifier

Thread Starter

teen devil

Joined Apr 6, 2009
47
Hi guys i am trying to build an ecg amplifier.. i am trying to build such amplifier which have
Amplifier gain: 250, 500, 1000, 2000, 5000
Bandwidth (-3dB): 0.05-500 Hz
Notch filtering at 50 Hz (can be switched in or out)
i am using
intrumentation amplifier = AD620

Op-amp = lm 741

when i am using simple function generator i am getting good amplification and also i can vary the gain for e.g my input from F.G is 2mV(p-p) with freq of 10hz and at output i am getting 10V(p-p) i.e. gain of 5000

but when i am trying to put a wav. file input of hearbeat with freq of 15khz its amplification is decreasing to gain 2000
i am using multisim 11 to simulate this . i am posting the circuit pics also .. can someone tell me am i on the right track or my circuit needs any tweaking .
will be waiting for your reply guys
 

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GopherT

Joined Nov 23, 2012
8,009
The Gain Bandwidth Product of the terrible, old 741 op amp is only 1,000,000. You are ok with 50 hz input, but at 15k hz, and gain of 2000, you are way over 1 million gain bandwidth product. Pick a more moder op amp.
 

Thread Starter

teen devil

Joined Apr 6, 2009
47
i ran the simulations again like i did it before also implemented 50hx notch filter when i used 15khz heart beat audio the results are in the pics
 

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