>> There are some jobs where you need to come withing spitting distance
>> of the correct solution to make it worth doing at all. This is one of
>> them. Use of very or very very =A0inferior opamps, unbalanced resistors
>> and out ofspec cap values is going to make life interesting.
>>
>
> I'm not saying that I don't believe you guys, but the fact that the guy g=
ot
> good results (http://www.eng.utah.edu/~jnguyen/ecg/bigecg.gif) motivates =
me
> to continue with this schemtic. He used 5% resistors, even.

Yes, even sows' ears can be used to measure heartbeat.
Also note the opamp comment.
He uses these.
Not overly costly at Digikey

           http://www.fairchildsemi.com/ds/LF/LF353.pdf

Try writing up the basic equations for the amplifier and plug in 5%
resistor values. It will 'work' but you'll  rather hope your common
mode signal is not high.


 R

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