Problem with ECG amplifier

[red devil]

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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[chuckey]

" input of hearbeat with freq of 15khz ", surely this is outside of its stated frequency response?
frank

 

[red devil]

i attached a probe on it it is showing 15khz u can also see in pic

 

[Audioguru]

The lousy old LM741 opamps are probably oscillating at 15kHz (built on a breadboard?). A heartbeat is at a very low frequency. Your circuit has two lowpass filters that eliminate 15kHz and other high audio frequencies.